I can highly recommend Ernest and Sergy. They just finished a major loft renovation at mine, and have previously done a cloak room and a front door. PM me if you want to see the quality of work! They were very fast and very reasonably priced. You can also search my post to see I had builders from hell before, so it took me a long time to find someone I can fully trust.
Sergy +44 7960 187935
Ernest +44 7876 566763
If you want to start April 1st I would start the conversation ASAP - good builders are always busy!