Youngalistai, I now have very tall gladioli in the garden - only a couple so far - as the corms get bigger, and therefore produce bigger stems, every year. You may be able to buy larger corms in a specialist garden centre but the ones you get in such as Wilkinsons take about five or six years to get that large. When I lived in Kent I didn't lift the corms every year - you should be OK in Surrey unless you're in a frost pocket.

I'd look on the net for suppliers, Youngalistair. They're probably selected bulbs just for the trade, but you should be able to find some. Annie