Moving internal plaster wall

We are looking to move an internal plasterboard wall to create a walk in cupboard in the main master bedroom.

Drawing of existing setup and dotted lines for new walls
//www.diynot.com/network/pody/albums/3034
Small room is an airing cupboard with boiler.

Who would be the best tradesman to get a quote from, carpenter?
Any idea on rough costs?

Im thinking I could tackle this job as diy, put up two walls, remove inner wall, doorway, skim and prob new lightswitch and fitment in cupboard.
Does this work require any planning permission or permit? and am I ok to do the electrics? (not needing signed off)

Many thanks

Is it your gas boiler in the cupoard or water heater?

Water Heater, pipes from this either go straight up to tank in loft space or down to Gas Boiler.

Thanks