hi I live in the uk and would like some advice on what is the best white chocolate to use for white ganache xxx

Well, I've only once made white chocolate ganache and it was hard to get it to dry was too soft.  If its just ganache you can get away with a cheaper white chocolate just being very careful with the heating of it as white chocolate is horrible for melting. I have Callebets but its not cheap and comes in large bags - I made a big order for a wedding cake  so I covered the postage. Most major supermarkets sell Menier in the baking isle.