I have just purchased a special needs mountain buggy from Nigel at Chariots (see here)
He was the sweetest, nicest, most informed guy you could wish to meet and further more he saved me £350. He insisted that I find out whether we are vat exempt for ds2 (I didnt think we were, noone had mentioned anything about it this to me) and also explained about Wheelchair vouchers.
A couple of phone calls later and a quick visit to wheelchair services and hey presto - a £200 voucher towards the buggy and over £100 saved in VAT.
I cant recommend this company highly enough and its not just special needs buggy's that they supply.