I've always found that normal tyre depots in UK are lazy and only provide a limited range of manufacturer's tyres and charge a lot of money for them, and why not when people only treat tyre buying as a "last minute" or "distress" purchase.
For many years now, I've only ever checked tyre prices on websites like blackcircles or mytyres - and then approached my local independent tyre pace to let them compete for my business, if they can't/will not, then I order them in from normally Mytyres.
Being mainland Europe based, Mytyres has access to many more brands, the most recent tyres I ordered in were for my daughter's late 2009
Ibiza 1.4 SC and they were Kleber Quadraxer all season in that "funny" 17" size. Actually I've just bought in a set of winter alloys with Goodyear winter tyres in 18" for her new Leon
Cupra from the same source.
I'd only ever buy tyres locally if I was stuck and had damaged a tyre.
In case that you don't know, buying tyres from Blackcircles or Mytyres etc is easy and these online tyre outlets have agreements with many local tyre fitter outlets, so getting tyres that you have bought online fitted is easy, most of these places will even ship the tyre order to your chosen tyre fitting outlet, so no messing with being at home to receive them and then needing to take them to your tyre fitter.
I'd like to support my local outlets, but most times with tyre outlets, you are really just being a charity when you consider the prices that are being charged, again as them need to
store them and normally you are not in a position to argue when you have a puncture, when it comes to just replacing worn out tyres you can have a choice if you can be bothered.