The engine is the "bullet proof" 2-5td BMW unit
LOL. "Bullet Proof" and "BMW" are not 2 phrases I would use in same sentence....
Right, trying to be more constructive, here are some things to try (yes, I have one of these crap engines as well):
Check waterpump - they have a habit of shedding plastic impellor fins.
Replace stat rather than drill it - helps to stabilise temp on these.
Check for coolant hose delamination.
Check for hot/cold spots on rad - these engines (and many other BMW plants) seem to sludge up rads after a while, causing poor efficiency.
Check electric cooling fans working.
Do a thorough coolant flush, use Forte cooling system flush.
Check if excess pessure build up in coolant, if it is, check for coolant leaks, but be aware these engines are prone to cracking heads (my current problem).
Hope that helps