Leather isnt sold by the metre. Being a natural substance it doesnt come in such easily quantifiable amounts. Its usually sold either by the square foot or sometimes square inch.
You can get leather pre dyed but make sure you get all you need at the same time as colour can vary slightly by batch, the usual way though is to get the natural leather 'vege-tan' and dye it your self to the colour you want.
In the UK the 2 best places are either
Leprevo or
TandyBoth are very helpful with advice as well as actually selling you stuff. I always use real leather for my projects as its very durable but if you arent used to working with leather (or dont want to) then leatherette/pleather might be better for you depending on your useage.
This does come on rolls like other materials being a manufactured material and the colours are usually more consistant too. If you want that type of material then a local shop or ebay
Red leatherette from ebay