Hi,
I have been researching about putting a new kitchen into my flat. Homebase seem to be quite resonable at 50% off cabenets when they have a sale but that doesnt include work tops, handles, installation etc.
I would not use B&Q I have heard some bad things about them ie. all the products not being delivered on time, poor workmanship. I would recommend you go with Ikea.
Out of all the kitchens I have researched Ikea is the cheapest even with homebase having 50% off Ikea are still cheaper. The cabinets are excellant quality and I think they come with a life time quarantee. They have an excellant range of styles and colours. I know it may seem a bit daunting designing where you want the cabinets, it was the first time I used Ikea in australia but it actually turns out to be quite good fun. I had ikea come out and measure up for me and it was fine.
Also with ikea they now do granite benchtops at a cheap price and they give you an overall price when you hand your design in of how much the whole installation will cost including fitting, plumbing, electrics etc. There is no waiting around 8 weeks for them to deliver and come fit it as Ikea have the stock already there and its just a case of waiting for the earliest date one of their kitchen fitters they use can come fit it.