I would say electronic transfer such as Interpay via banks is probably the best. A draft is safe but if it should get lost there would be quite a wait for it to be replaced.
The rate is set on the day and then you lodge the money into their bank account. It takes a few days and there are no charges if you send more than equivalent of £3000.
How much are you talking about - and do you have a bank account here and in the UK?
You could let the bank do it - but you will probably not get the best exchange rate and they may add on other charges.
There are currency brokers who do it if the amount is big enough - or if it's regular payments.
A small percentage difference in the rate could cost you hundreds on a big transaction.