Tyres near Wakefield

Just got back from Cadwell and had an excellent day except my mate high sided in the Inters and smashed his CBR600 to bits! (He's OK just a swollen ankle and a bit of a gammy finger). So to the point of this post....
My rear tyre has now completely had it, came in after the second to last session and noticed that it was down to the carcuss in the middle so couldn't go out again.
As this will be the first time I've replaced any tyres on my bike i have a couple of questions:

1. Can I just replace the rear as the front seems to have loads of tread left?
2. Anyone know any decent and reasonably priced tyre places in the Wakefield area I can take it too?
3. Can i / should i mix Tyres? I have Dunlops on at the moment and was thinking about changing to a better / grippier tyre.
4. If i change what would be a good tyre to go for? (I'm not made of money at the minute, I do quite a bit of road riding but have 2 track days over the next 2 weeks too!

Any advice would be appreciated!

Also spotted an SV1000 there today, not sure if they were riding but No. plate was S100 SVS (nice touch). Anyone know who it was?

Cheers.

[Spikenipple]

Can't go wrong with a Pirelli Diablo Supercorsa, probably SC3 compound if you're doing a lot of road riding.