WM Camping have a fantastic selection of groundsheets from major manufacturers such Vango, Kampa, Outwell, Easy Camp and Gelert.
We would always recommend purchasing a footprint groundsheet for whatever tent you buy. A footprint groundsheet helps mark out the pitch of your tent and also helps keep the underside of your tent clean. So when you come to pack away your tent it's the footprint that is dirty, not the tent.
At WM Camping we feel the best reason for buying a footprint groundsheet is that it helps protect the underside of the sewn in groundsheet on the tent from sharp stones etc. A footprint groundsheet is much easier to fix or replace than a groundsheet that is attached to the rest of the tent.