I've never seen it growing in very wet conditions. I have always though of them being for more dry conditions. The RHS site which is the cultivation 'bible' says for well drained sites. so they wont sit with wet roots and be happy.
google pampas grass but click on the RHS advice page.

RHS was the first site I looked at Seaburngirl, thankyou :) I have pampas on the opposite side of garden and I was really hoping to have some on the boggy side :( I did think as much regarding the wetness so I guess it's a definite no no, back to the drawing board for me then!

The name says it all - the Pampas is dry grassland.

This is an American site but does list the zones the plants are suitable for so might give you some ideas:

http://hoffmannursery.com/home/the-plants/search-results/?preset=14

Or try Ligularias

Also, any site that is friendly to Hostas is unlikely to have enough sun for Pampas Grass.

My hostas are actually in full sun all day Tugbrethil. They have been in situ for years and thrive in my garden in sun or shade. Have Ligularias already thank you, Steragram, was hoping for something more permanent over winter.

There goes my parochialism, again! :/
Here in the States, Hostas are generally considered shade plants,with only a few varieties doing well in full sun. The exception is in the Pacific Northwest, where the climate is similar to the UK. Here in the "subtropical" desert, they are just barely possible in shade!