If these payments are made from withing the EU, Euro-denominated credit transfers (wire transfers) inot UK accounts will not cost more than an intra-UK credit transfers up to an amount of € 12,500 per transaction, even if your UK account is Sterling denominated. Conversion rate will be the "interbank rate" (i.e. pretty good). The threshold of €12,500 will be revised to €50,000 as from 1 January 2006.
See
this document (Article 3 on page 3 is the one you want).