UPDATE: Today i decided to check the air filter, pretty clean. so i moved onto the carb to head rubbers. I took each one off had a look and even though they are cracked real bad on the outside, it has not penetrated all the way through. Back on they went. I then took the carbs off and holy shite the float bowls were full of rust. So i cleaned all the float bowls and all the jets (we have a blanker mid jet that fooled me into thinking it was blocked for a while) and then had a look at the diaphragms and lubed up the slides. I also decided to reset all the air/fuel mixtures screws as the idle was bad beforehand. That was a mistake as one of the screws just snapped off. So i had to cut a slit in it to be able to turn it... anyway that sorted i put it all back together with a new fuel filter and now it runs perfect again. So i'm guessing it was blocked up carbs or something carb related. Just a side note, two days beforehand i put in a small amount of carb/injector cleaner in with my fuel. I wonder whether this had a part to play?
Cheers for the help.
Cheers for the help.