If you going to pay some to do it then you looking at 2k+ I had all my engine work done at Stealth Racing..... people have said that his rollers run a bit high, I had 190. something (says on my sig) and I had the car run on another set of roller (westec) when they were open and it pulled 190bhp there as well.
I got 268 Schrick cams, p&p head, 3 angle cut valve thing lol and then a remap.... the car rev's to 7.5k now and from what I have read that is bascially the limit the bottom end can take!
Car's like Clio 182, etc.... don't keep up, the 1st night I had my car back from stealth racing I had a scooby pull me over asking what was in my car because he couldn't catch me. And as a track car, it's more fun than I ever had in the car!! Totally different to what it's like on the road!
MPG...... well, I now class 22mpg good and drivin thru town (stop and start) I have seen as low as 16mpg, on the motorway going at 60-70mpg I can get 32mpg.
I would say get a 4-1 manifold 1st and wiv the decat it should go well! Or you could look at the cheaper options 1st, 3.94 final drive, lighten flywheel? Them together cost me £570 in total thats wiv a new final drive but I do know a mate that rebuild gearboxes so had that done cheap!
Think of getting a LSD (well ATB diff) I managed to get a peloquin one for £545 but can't tell you if it's any good yet because my car is still on axel stands lol