Loads of websites allow you to send stuff to an address other than the invoice address, although I don't know of any clothing ones specifically, but try Jojomamanbebe / Verbaudet or similar
Alternatively the Tesco delivery service will allow you to deliver to a different address - a friend of mine once sent me some bottles of wine and chocolates this way as a surprise - but I don't know if you can buy clothes from Tesco online.