AJL turbo upgrade options & expectations?

So I've a few pennies to spend on tuning the engine of my AJL TQS.

The car was shunted from behind a few weeks ago and I've just recieved a nice fattish cheque from the insurance company. The rear bumper / tow bar and boot lid need replacing but I've got my eye on replacements for those already.

So I've got about £1k to spend on the engine / tune. I know that £1k won't go very far but I'm hoping it could, at a stretch include a KO4 turbo without getting all the other things done i.e. FMIC, injectors, exhaust etc etc. I'll be doing the bulk of the mechanical work myself so other than the tune it's parts only I'll be paying for. So...a few questions to those in the know.

What can I feasibly expect to pay and get in terms of hp/torque for the following upgrades:

1. Standard tune with stock exhaust & KO3 turbo (£300-£400?)
2. Upgrade to KO4 turbo and associated tune with no other upgrades (£1k?)

If some more pennies became available, which they might:

3. Upgrade to KO4 turbo with new exhaust (£2k?)
4. The above inc new injectors / FMIC (£3k?)

What else should I be thinking about?

Thanks Aragorn...more reading to do now. From memory, you're fairly local to here (Glasgow) any recommendations as to where the best tune could be obtained from?

slepy, thanks too. I;ve read this post before but it's all tailored towards everything other than a AJL engine.

Thanks Aragorn. Spoke to Rick at Unicorn so have a plan forming!