Its really nice to get great service from people and here are some people that I would recommend you try
Mel The Terrain Tutor - I just like what this guy does - link here -
eBay - love it or loathe it - I love it. There are some great traders - look for very high feedback scored and descriptions of stuff that sounds like the person knows what they are talking about
Two Fat Lardies - a recent discovery and a very good find!! Check them out (site details in the LINX section)
Hattons - They advertise themselves as the largest model shop in the UK but I went there recently and its just a warehouse!! That aside, they have a massive stock list and great website. ALL my railway stuff comes from them as they are always on the top line when it comes to price and delivery. Highly recommended
Grubby Tanks - sent an email regarding their AFVs recently and got a very cordial reply prompting an order. I cannot say anything higher than that!!
Britannia Miniatures - part of grubby. Good range of models and a very user-friendly website. Ideal for technodinosaurs like me!