The store is called Fireworks Direct. I'll obtain the proper address and phone number and post later.
They had single ignition boxes for £35, £50 and £70. However, all their stock is now half price so make that £17.50, £25 and £35. From memory they lasted 49 seconds, 73 seconds and 97 seconds respectively. Now, although this doesn't sound like a long time, we had one of the "cheap" ones and it was fantastic. Probably the best non-profesisonal display firework I have ever seen. It may have only been 49 seconds but it felt like much longer as it was 49 seconds of intense bangs, flashes, sub flashes etc etc. It lit the whole sky. I'll certainly be going back for more.
We also got some other multi shot cakes, reduced down to £5 and £8 that were good too. Their mid range rockets were good value when reduced to £6 for 4 but the big rocket we bought (was £24 reduced down to £12) was a bit of a disappointment. It stood 6'6" on it's stick and the actual head was 13" long. It went up like a space shuttle, probably into the Heathrow flight path, and left a 12" wide burnt ring of grass below it but it only resulted in one large straburst with a decent bang. A very good rocket but with it's size and initial price we were expecting something really special!