Presuming you want it tippy-top straight away, as opposed to waiting for things to wear out, with £1,000 I would:
1. Engine out.
2. Replace engine mounts.
3. Have the bottom end checked out. If it checks out okay probably just have the rings replaced.
4. Very light head skim, replace valve guides and stem seals.
5. All new gaskets throughout.
6. Have the engine decoked (steam cleaned) while your at it.
7. New oil pump, thermostat and maybe the water pump too.
8. Paint the engine while its out. POR15 paint is recommended for the block.
9. New sump gasket.
10. Change gearbox oil.
11. Assess the clutch for wear and tear - its cheaper to change while the engine is out.
12. New injectors (bosch brass/merc ones) and injector seals.
13. Obviously a cam belt and tensioner change plus all aux belts while your at it.
14. Check temp sensors on the side of the head.
No.3 to No.5 are the more important one's. Search for info on the idle issue - its common but easily solved.
Happy spending!
David