OK UPDATE
I've phoned my local stealer - a new washer is £5.50 so I've got one on order. The axle was £45 excluding all washers and nuts (I can't justify that cost at the moment) plus mine seems straight and works fine.
So, 2 things now. Bodge the current washer to get me to Brighton on Sunday!!!
Work out what 117Nm on my torque wrench actually is..... but like I said, I've never had this issue before, plus I had never adjusted the chain myself since I've owned this bike. It's had 2 rear tyres fitted by two different garages though, I'd like to think they are doing it up to the correct torque.
So I'm thinking my wrench is prob about right, I reckon the washer that was on we getting knackered from 14 years on the bike. I reckon the one I bought from a chap on here was even more shit than the one I took off.
So moral of the story, stop being a tight cunt by paying £6 inc postage for 2 washers of unknown quality that are crap and just pay the £5.50 for a brand new one in the first place, because it's now cost me £11.50