Hi Matty1 and welcome,
If the T/C is already well fitted and in good order, you can get quite a lot of bhp from it. (I think the record for an 8v, turbocharged is 395bhp - more for a 16v). But parts are getting a bit expensive.
On the other hand, if it's knackered, it could be more cost-effective to change to a more modern engine with cheaper spare parts. If the XE then you'll probably have to notch the front member (JLH does this though his speciality is Zetecs) to fit it in.
You might find this thread useful..
http://www.morrisminoroc.co.uk/index.ph ... ic&t=10557