I am not much familiar to the companies who are good in the Uk, they can be seen in the comment above but I can tell you or guide you a bit about what defines a good company from which you should buy the furniture. For me msofas.co.uk was which made me come to this conclusion
The company I would recommend you to buy from is which has the products from the healthy products. Harmful chemical instilled products are never a good idea for your house especially when you are living with kids.
The furniture company should be selling a lot of varieties in every depart. A 2, 3 different kinds of things is fine but I will prefer one furniture of at least 5 kinds like, sofas.
I will go for the furniture shop which has been in the market for same years. Though, sometimes you get good product from a new company but a company which is old and successful could be the ideal choice.
The company should be having some branches. This can be linked with the point above. I mean if the company is successful then I am sure they will launch new branches
I hope form the above points you are going to learn a lot even though they are not totally answering your question but I am sure it will help you immensely