Thank you unfazed 
I know the coolant pipes clip on with spring clips, was wondering if there are any more O-rings apart from the fuel connecting pipes. If I am splitting the carbs apart from each other I may as well replace everything O-ring wise.
Also had a quick Google search and there are a couple of bearing suppliers local to me as well, so I can give them a try.

Just an update, finally managed to get the carbs back on the bike (been really busy for the last month).
Turned on the ignition and the fuel pump ticked for a good few seconds while it filled everything up, then stopped as it should. So better than it was before stripping and cleaning the carbs out, fuel pump would just constantly run as one of the floats was stuck with gunk.
Could smell petrol so didn't try and start it. Had a quick check/look and I have a fuel leak, looks to be coming from between carb 3&4 (TPS sensor end) and higher than the float bowls. Now wondering if it's leaking from one of the fuel link pipes between the carbs, do these have O-rings between the metal fuel pipes?

Left the carbs complete and just cleaned the guts of each carb and replaced the O-rings and float bowl gaskets. So a bit unsure where it's coming from exactly.
Looks like the carbs will be coming off again. Is it possible to pull the carbs out and hook it up to the fuel tank pipe? It leaks when you switch on the ignition and the fuel pump pressurises. Would make it a lot easier to find the leak.
EDIT: It's not leaking from the overflow pipe, which it was doing before stripping and cleaning out the carbs.

So the carbs are all cleaned out and back together again. Good job I ordered that O-ring kit as my Dad checked his order for his ones and they are not Viton, just standard Nytrile. The old ones were absolutely knackered, rock hard and some fell to bits when taking them off to replace. No surprise really as they are at least 24 years old.

We just replaced the O-rings inside the carbs and new float bowl gaskets. The jet cleaning tool and brushes came in handy, I was very carefull to try and not enlarge the holes in the jets etc.... got a good amount of green gunk out even after carb cleaner and ultrasonic cleaning from the little jet holes. A toothbrush came in very handy as well as you can clean everything without damage.

We checked the float heights, all seem to be the same height and parallel with the carb body when just resting on the little float dodahs. Left them well alone as didn't want to make it worse, hopefully they will be ok. Bike has only done about 18K ish.
This afternoon I cleaned out the blocked hole on the bottom of the fuel tank, was blocked with crusty gunk. Does anyone know if one of the tubes is a breather and one is overflow from tank? I had the tank leaned on it's side with fuel tap to the right, and a little bit of fuel came out of the bottom tube.
I have a little bit of new and old fuel still in the tank so I wacked some Redex in there and was giving it a good shake around, can't see any rust through the fuel filler cap. I will chuck this out before fitting and put some fresh petrol in.

Also fitted a new fuel filter and I have a new upgraded front sprocket nut, never checked it but for a few £ I will just swap it anyway.

Will probably have to wait until next weekend to put the old girl back together again and see if she comes back to life. I don't have carb balancers so I will probably have to take her to a shop to get set up. Could probably do with a new chain kit as well tbh, I think it's still the original but it got a bit rusty in the garage the other year. Also need to bleed the brakes....and whatever other jobs come up 

Thank for replies
Just quick update: No wonder the old girl wasn't happy looking at the state of the carbs.

Took the carbs apart and everything was completely covered in green gunk and that hard to shift varnish type substance. The jets were mostly blocked, gave everything a good clean with carb cleaner then took it to my parents next door neighbour to put the bits from float bowl and jet needle side etc in his ultrasonic cleaner. We did this one carb at a time so not to mix up parts. Not sure how but managed to lose the small spring that goes on top of the jet needle. Can't find spares so had to rob a spring from a biro pen and cut down to size, it only holds the needle in place so it doesn't move.
After ultrasonic cleaning everything had a good gong over with carb cleaner and a toothbrush, and the jets were cleaned out with proper jet cleaning files.... different diameter metal rods. Amazing how much green gunge came out the little holes. The carbs were cleaned with some "gunk" and a toothbrush then had a good going over with carb cleaner.

Just ordered some new float bowl gaskets and a fuel filter so all the bits are in seperate labelled up tubs. My dad had the other seals, good job as they were knackered as well. Rock hard and starting to split. Hopefully once it all goes back together and I clean the tank breather hole out it should run alot better. I don't have a carb balancer so will have to see how it is after, might have to go to the bike shop for that if needed. I know you can buy cheap balancers but not sure if they are very accurate.
Next door neighbour who fixes up lawnmowers and anything with an engine said he has never had so many issues with carbs since they went to ethanol mix fuel. He basically said if you use standrad fuel then use a fuel treatment with every tank, and if not going to be running for more than a month or two put high octane petrol in the tank first. I think Esso go faster juice is supposed to have no/minimal ethanol in it.