Focus, even VW admit to using it as a reference point for the new golf rather than the previous golf! Though TBH cars are cars, not exactly worlds of difference these days. Test drive and pick one you like.
Look at whats included in the contracts.
Work pays for fuel but not serviceing/breakdowns, get a petrol.
Work doesn't pay for fuel but does serviceing and breakdown costs get a diesel.
Work pays for everything, whatever you want.
Diesels do more mpg, but has several £1k+ components to fail that a petrol doesn't (DPF £700, DMF £800, Injectors/pumps £???, turbo £???, where ??? could be £500, or could be 10x that if the turbo spills its guts into the engine).