Personally, I'd probably be buying the Kumho Ecowings. I've a set on my Volvo that have lasted 24,000 miles so far and are looking likely to last a good few miles (I'd reckon another 24000) more. Good grip too.
Pretty sure I have Toyo on my MX5 and they're good too.
Have to question the logic of buying tyres from Asda though! Support a local independent - mine gets better prices than most online places