I think you'd struggle to get a 16i or fiesta supersport for £4k that were worth keeping as an investment car.

Maybe a Mk5 escort RS2000 4x4 but that would be a struggle to get an unmolested low mileage minter

Other makes that you might get in the £4k bracket

Fiat X-19
MR2 mk1

106 Ralleye
205 Ralleye

Nova 1.3/1.4 SR

Cavalier Club

Calibra Turbo?

Renault 19/21 Turbo
Renault 5 Turbo

Uno Turbo