In my experience, the Royal Mail postal service is really great. For being across the pond, they have excellent speed and prices. Its kind of unnatural actually compared to Canadian postal speeds and prices which are both worse, in my experience as well. Someone said in another thread they figured them out, so mebbe those days are over though.
So, even if you do pay shipping, I'd say the prices would prolly be at least reasonable. Thats also based on experience thats a year old, but hey...
Total offtopic side note, but, you don't talk to enough british people if your having issues... It does grow on you.

My new hobby is an online game thats full of brits and folks from wierder countries, and we speak (use audio) all the time. Some are truly hard to understand for local coloradoans, apparently I just got used to it. Also of note, in my experience the more rural areas of the UK (say, newcastle, got a buddy from there) are easier for North American english speakers to get, while the more developed areas (London) are influenced by 19th century slums and have thicker british accents.
It used to scare me to call Forgeworld or the Royal Mail. I'm not sure why, could just be the isolation of my little town.
My thoughts at least.
-Zack