Sounds too cheap to me, hard to say without having seen the property and getting a feel for it but roughly I would have thought more like £4kish all in if you're plastering up and everything too. It's got to be worth you doing it though, and only you know how much you want from the job. I can't imagine after paying everyone and your materials you'd be left with much from £2.5k. Also bare in mind that something WILL go wrong on a job like that and suck a few hours that you hadn't accounted for and there's a good chance you might get a call to ask something or something tripping after you've gone that you need to see the customer about and might eat up more time with no pay.