My first question is what stage is your car?
If you are max 250bhp the recommendations already giving is okay, but as you climb the power ladder, you need more grip, at least up front. I would avoid Continental, Michelin PS3 is okay for this level and GY F1AS2 at the top of this class
From my personal experience running above 350bhp for a couple of years my recommendations would be the Michelin Pilot Super Sport due to the great balance between grip and mileage. Trouble in 18" on these is the loadindex which is 88 and as i understand can be an issue in the UK. The 235/35-19" should be okay regarding loadindex (I'll have to check on the missus car as she has them fitted atm) and are well worth the money.
alternatively the Toyo R1R is a great contendent as i saw more than 15.000km on the front in size 225/40-18".
Remember a harder rubbercompound might have a higher treadwear and should last longer BUT if your power ends in wheelspinn your harder worn tyres might end up lasting shorter than a more sticky tyre that actually gets the power down to the ground