Hi and welcome to the forum.
I haven't ordered clothes from the UK yet but I have ordered, without problems, from QVC, eBay, Amazon and Argos.
Next, although having a Spanish division, only deliver to mainland Spain at the moment.
Zara of course will deliver. Not sure but I think TKMaxx or M&S may well deliver. House of Fraser quotes that they will too.
I think your best bet is to search for the website of any of your favourite stores and check to see their delivery areas.
Of course if you have any good experiences please let us all know