Yes but the ones in B&Q dont exactly match up to size and there is nothing in the existing wardrobe to fit shelves. I guess I will have to do DIY to make holes and saw off the shelves to exact size or get a handy man ?
Unless the built-in wardrobes are by an established manufacturer (and fairly recent) you may struggle to find shelves that fit. You may need to get pieces of board or wood cut to the right size and then fitted using batons. You could do it yourself, but it is quite a tricky job and may take you a bit of time if you're not an experienced DIYer. £300 may save you a lot of swearing.
Well, if you want to tackle it yourself, you'll need to make sure they are cut to size, attached properly with brackets that can carry sufficient load, you'll need to tools to make sure it's all level etc. So it's an easy enough job for a DIYer with some tools but if you're a novice and don't need to watch every penny, then it might be nice to just get someone in to sort it out quickly and well.
you can order panels cut to size in various board - they will do the cut edges as well. I got some to match kitchen cabinets. Very happy with the service. I'm sure there are other suppliers doing a similar service. The stuff I bought was Egger laminate, which is superior to the stuff sold in DIY sheds, and the cutting and edging was better. 18mm is a suitable thickness.
you download and fill in their spreadsheet and it calculates the prices. It's not working on my pc today. There is a minimum order charge which I can't remember.
There are also companies that will make wardrobes and kitchen units to order in the dimensions and finish of your choice, but they may cost £hundreds each. Kitchen units I've had vary from £71 (small) to £178 (large) plus delivery, I presume wardrobes will cost more.