Hi there matty and welcome to TorqueCars. Nice to have you along. I did some time on a Rover 220 GTi and loved it. You have the newer shape. There is not a lot of point turboing the 1.4 to be honest. They are pretty stressed engines and put out quite a bit of power for their size thanks no doubt to Honda's input. Your best bet would be an engine swap. The 2.0 T series engines will fit as will the 1.8VVC lumps.
A turbo will typically cost around £3000 to buy and fit and probably a bit more in fiddling to make it work. Moto-build racing did a turbo on a 1.8VVC but they had some reliability issues.