plus another £70 if you include the RAC membership
Tell me about it. I had to join the AA when my car broke down. Then had to 'upgrade' my membership to get it towed when it broke down (Toledo). Then to rub salt in my wounds i had to pay £99 to get my
Ibiza towed after an accident because i only have 'breakdown' cover. WTF

I hate breakdown companys now. Lol.
Hopefully won't be another situation like so many I've read on this forum where people end of replacing about 20 different things before they fix it

!!
I know what you mean. I did something like that. Took it to local garages insted of taking to to SEAT in the first place. Wasted £60 and nearly got conned! It's VERY tempting to think "Well i'll replace this and see how it goes." "Ok that didn't work so let's try this..." LOL
Anyway - I think it's the spark plugs mate. Have they been replaced? It could also be a vacuum leak at the throttle body, inlet manifold or associated hoses, but the RAC should have checked this. If not then it's probabaly blocked injector(s) or a fuel injection fault.
If it was me i'd try replacing the spark plugs because they're cheap and easy to fit. If that doesn't fix the
problem find a specialist VW garage and ask them to check the car with Vag com. When you phone them make sure they only charge £20 for a scan, then when you get there tell them to let you know if they think it will cost more. Only because i was told it would be £20 for a scan, and when i went to pay they charged me £40 coz they said they had to do 'deep diognostics.' They didn't even find the
problem!
Also, if they tell you something else needs doing ignore them unless it's obvious. A VW specailist tried conning me telling me my clutch needed replacing. It's always best to get a 2nd opinion.
Hope you get it sorted mate.