thats what i do mate, i use halfords oil filter with 10w40 oil super s all from halfords (tradecard). spark plugs from tm development or tuning development which i think are cheaper then burwash.
We kept it as semi as that is what most people use and the Fuchs/Silkolene is one of the best. I would only use fully on a forged build or track car that is running hotter oil temps
i run fuchs titan race oil fully synthetic 10-40, and its never let me down on track.
and halfords filter, jesus there nt as good as the blue print ones , which are cheaper.lol
servicing is important mate and if u use cheap products then the car will suffer.
I was highly recommended shell oil! Full or Semi.... full for the winter, semi for the summer! Fully synthetic would not be very friendly with your engine/turbo seals by the way.
If you buy cheap oil/filter change it very often and I don't see any problems with that (as long as it's not in the cold winter).
Have TOTAL in my at the moment, will try Shell for the winter!