They include everything in the price: Product + shipping + taxes.
They don't include VAT and import duty - they used to 'guarantee' you would not pay it, by marking the parcel as a 'gift', and refunding you if HMRC (customs) caught on, but they are more reputable these days, and HMRC have got wise. In any case, this is illegal.
I don't believe there is import duty on camera bodies (only lenses) but you will certainly pay 20% VAT on delivery, plus a handling charge from Royal Mail or whoever the handler is - normally £20 or so on top. If you don't pay up, you don't get the goods.
If you work it out, prices from DigitalRev are therefore higher than the UK at present on a 5D3.
They are nice, reliable people though.
Of course this advice applies to all non-EU vendors when you are importing into the EU, for example Adorama, B+H, etc.