<3 Pirelli P-Zero Rossos. I've had them on my car for years now (same 235 fitment as you Beezer). I didn't notice the difference in fuel economy when I got them!
Bit of a strange one eh?
Originally the car came with Bridgestones on 17''ers, then the BBS VZ033s off my MK5 went on there with Contis, followed by Black Detroits wearing FK452s which all gave similar fuel economy readings brim to brim. The Pirellis have admittedly only been on there for a couple of weeks including a touring holiday but have definately made a tankful do a lot less miles. In theory the touring should have yeilded better consumption as it was all easy low rev driving, no stop start, no traffic jams etc.
Should be doing a good few hundred miles this coming week so will see how I get on.