although play247 are decent enough (particularly if your looking to get a film delivered within a couple of days) they don't have the best range or prices of Region 1 titles as they usually tend to sell only goods under the 18 quid customs limit
i would say that on the whole
http://www.dvdboxoffice.com are the best place for Region 1 - great prices on the majority of titles/free worldwide shipping/very little chance of customs as they bulk deliver to europe - the only bad thing is that they can take a while to get hold of titles if they are out of stock (otherwise delivery is usually about 6-10 days)
maybe also take a look at
http://www.absound.ca - another canadian company (like dvdboxoffice) with great prices, although you do have to pay shipping charges and you
are more likely to be caught by customs if you go over the limit as absound always declare the true price of the package
i would also definitely recommend that you take a look at some australian dealers (i've used
http://www.chaosmusic.com and
http://www.dvdcrave.com recently) - the oz dollar is really weak at the moment so the prices are fantastic seeing as their normal prices are decent anyway, and shipping from both the above sites for me was only about 4-6 days!
australian (R4) discs are also on the whole very good, sometimes having the best bits (eg. extras/uncut) of the equivalent R1 release and the higher resolution of our R2 PAL discs (although not always - but it's always worth checking the R4 disc before ordering R1 or 2 - i'll post a couple of good region comparison sites for you later if i remember)
R4 packaging is also sometimes better than the R2 (no cardboard Warner snapper cases for one

) and also they don't have the 'rental window' which we now have in the UK, so you can now buy (for example) Scary Movie from australia while you can only rent it over here.. oh!, one last point is that quite a few australian R4 discs are also compatible with R2 players (ie. you don't require a multiregion player to play them) can't remember where, but there are a couple of sites that list which discs are dual/multiregion like this
hope that gives you some pointers to help get you started!!