As I'm totally fed up with the fact ds2 has gone through YET ANOTHER pair of expensive shoes rather than grown out of them, and remembering Califrau's thread about how fitted doesn't mean necessarily mean good quality, I'm looking at buying non-fitted shoes for the remaining term.
I found some really useful things while researching on the net about it, so thought I'd share in case anyone else is thinking of doing the same.
Startrite online now sell foot gauges for children here - £5 for the small gauge (approximate age range suitable 0-3 years) and £7 for the large gauge (suitable around 4+ years). They also have really helpful instructions on how to fit your child's shoes with a video here.
Unfortunately, their gauge gives the reading in mm rather than in shoe size (cheeky!), probably to encourage you to use their website to convert using their fitting calculator and then go on to buy their shoes from their site. However, there's a really good conversion chart on Wikipedia (just scroll down to the bottom and skip all the mathematical equations section!) which means you can bypass all that.
Hope this is of use to someone else too