Unfortunately I don't know any wholesaler in the UK who sells heart and other balloon frames. Apart from doing a Google search, your best bet could be to go through the list of wholesalers provided at Nabas: http://www.nabas.co.uk/search_results.php.
NABAS is the only independent trade association for the party and promotional balloon industry in the UK. When searching their members, you can specifically search for balloon manufacturers and wholesalers.
Good luck for your search. It would be great if you let us know whether you found a good wholesaler in the UK.
