Hi mate, since you have a spare set of wheels, I'd suggest you go with a proper R comp tyre.
Mid 400's will definately get you a Kuhmo V70A, and yes I'd go with a hard compound. They're a good tyre although not the cream of the crop, they seem to have moved on a little since this tyre was developed.
The top tyre right now in my mind is the Dunlop 03G, and I'd suggest an "SR". This compound is between a medium and a hard. They offer similar grip to a hard, but heat up a little quicker. Back to back, same car, same day, a HARD Dunlop was exactly one second a klm faster than the hard Kuhmo. The Dunlop is dearer than the Kuhmo, but I think you should still get for under 500.... I just ordered a set of 235/45/17 and found them for 420.
I'm not sure if you're allowed to run them, but it could be worth seeing if you can use the Silverstone S575. It's a quick tyre, but not elligable for tarmac rallies, except ARC. It's relatively cheap too so worth asking the powers that be.
Cheers, Ben