Flour, and things

If you are providing food that is homemade for a Coeliac here are some commercial products which are safe for us to use:

Flour
Doves Farm Flour that is marked Gluten Free, usually found in the Free from section of most supermarkets.  Be Careful though as Doves Farm also produce ordinary flour, which will be in the normal aisles.  Their products are usually marked clearly Gluten Free and as such will usually be found with the other Free From products.

DS (Dietary Specials) Gluten Free (Frozen)
Sausage Rolls
Shortcrust Pastry
Pizza's
Garlic Bread

Bread
All in the freefrom aisles
Genius (is one of the best)
Warburtons
Yes You Can

Marks and Spencers
Marks have all their Gluten Free products on the shelves with the ordinary things.  Very recently they have just started to package a few items in green for their made without wheat range.
This is the place for Gluten Free Sausages they do all sorts of flavours, and that includes their cocktail sausages.  They also have Gluten Free breaded fish and chicken.   They use their own crossed grain symbol (it will be found where you would find the freezer symbol etc) and it is a little ear of corn with a line through it  in a pale orange colour, but I would still check the ingredients, so far no problem.

Other known brands for gluten free that are readily available;
Mrs Crimbles
Genius
Glutafin
Trufree
Prewetts

FREE FROM supermarket own brands (Tesco, Morrison's, Sainsbury's, Asda, Waitrose, Co-op)
Biscuits*
Bread
Cake

*Be careful when buying supermarket own brand biscuits, many now contain Gluten Free Oat Flour and some Coeliacs can become very ill if they eat this.  Even though it is labelled gluten free, Oats contain a protein that is very similar to gluten and can cause a similar reaction.  Again if in doubt, ask.