As in Brazil, appreciating trip-hop is not an easy thing in many countries (lucky you, on this case, if you are British, so things might be easier to you). Most artists don't release their albums around; just mainstream artists — as Morcheeba, Massive Attack and Portishead — do release their albums almost everywhere. A good tip is to visit the official websites. Many artists are independent or work with smaller labels, and do commercialize their albums by themselves, or using online services (which makes the CD be cheaper than ordinary prices at conventional CD stores). U-topia, for example, did produce themselves their first 2 albums; you can buy them getting in touch with the band, through their website. I don't know how the prices are now, but sometime ago you could get them for EU$ 5 (each one) + EU$ 4 for the shipping. Which means: you could buy both CDs for just EU$ 14! Very cheap indeed, specially if compared to the prices of conventional CD stores (even more when the CDs on those stores are imported, what's the rule for those stores on many countries).

About mp3, the tip is also to visit the official websites. Many artists make some tracks available for free downloading (specially new and underground bands). From the Glorybox's website, for example, you will be able to download a whole demo album. From the site of Mensch you can grab their both singles.

I reinforce: many, many, many of the best artists you'll find out on the genre are independent or work with smaller labels. So keep in your mind the best thing to do is to visit their websites. Also, supporting those artists and buying their albums is a good way to help keeping it all alive.

A very good website to check new artists, independent artists and smaller labels is cd baby. You'll find a lot of good music in there.