Ds2 isn't starting school this year (he misses the cutoff date by 8 days!), but I will come on here and cry with you because I will be imagining what a state I will be in in a years time 
Fizz - I haven't found a cheap shoe site as such, I just tend to trawl the sales. Jones often have good sales, as do John Lewis. Or if you know what shoe you want I search for it online, but if it is current season you often can't find it cheaper than it is in the shops.
Brantano stock older seasons Clarks I believe, I don't know what kind of price they are though. I also think Clarks are over priced because they are often synthetic materials rather than leather. I have found the Clarks sizes to be more generous than most other makes, in width and length.
The Kickers website often sells off old stock at a good price, but Kickers tend to be cut on the narrow side, so often not good for little pudgy baby feet.
I know too much about children's shoes don't I?
Ds3 is a 6 and will probably be a 6.5 or 7 by the time he goes into winter shoes. I have raised a family of Big Foots 