Duncan McCaffray
Difficult to quote a price without seeing it and discussing your expectations of the job. What quality and price of materials you source. My advice is get someone who either has in house multi trades or has access to these guys to quote job. You may need a builder, for walls if load bearing, joiner, plumber, tiller and spark. Some days all the trades may be on site with four guys wages to pay for that day. An in house Multi trades company will probably be more expensive than using a trusted guy with contacts. Costs nothing for you to post a job on rated people and get 3 quotes and take it from there.