Question -

If it was spark plugs which is a main part for SPARK ignition how would this effect when warm? Unless there not working which means a miss fire and no spark = to not running. how can it change or diffa when warm. So to answer that it wouldnt start or run if there not working correctly.

My first option would be to get it checked out on a comp. This would show the problem for a sake of 50pounds.

So it boost's fine untill warm. I wouldnt say its a boost problem as such. HTleads wont be ur problem nor ur plugs. If it was ur dissy cap then it wouldnt boost whats so ever, boost leaks = no boost and emmisions is ur fueling which is no relevence to your boost but can effect the timming and running of the engine.

Anyone can say, man try thus but i would take it to an expert who knows whats wrong as no offence ment to anyone on here but my advice is to take it to be tested as it could be anything.