At skuzzle motorsport I offer such conversions. If the kit is good, then £1000 is more than easily achievable, but if the kit is poor and parts need modifying and fabricating, then it is a little more pricey.
To give you an idea, I can source and fit intercoolers for under £400. MegaSquirt ECU (which you are going to need to control the fuelling and ignition timing) for under £600 fitted and if its 10 hours to fit the turbo (not likely that long) £400 labour to fit.
What I dont like doing is supplying turbo kits. There are too many variables and im yet to find a perfect solution that everyone likes, therefore I leave the turbo, manifold and downpipe to the customer to find.
You will want to factor in a possible clutch and brake upgrade too though if shooting for more than about 160bhp.
Skuzzle Motorsport - MX5, Prestige and Race Car Specialist and tuner. Just bought a Dyno in Winchester.