Based on what you're describing and with out seeing the work required or measurements you would be looking at around £160 for labour. But that is based on my own day rate and it's likely to change as you would need to provide more information. To replace doors and alter shelving is simple but when cutting into framework and altering which it seems you want to do, then the costs go up and the materials do too.
If you were to have a new built in wardrobe it would possibly work out cheaper. I recently did a quote for a potential customer for a floor to ceiling built wardrobe which measured roughly 1.5m x2.4m x 0.5m which was solid wood, it came in at just short of £1,000.
I hope this helps.
SHS-Scotts Handy Services