Hello, looking for some advise on where to go with my 98 2.5 Diesal.

Recently the car overheated so took it to my usual garage.

Symtoms - Doesn't overheat on tickover unless left for 30mins plus, but as soon as you drive more than 3 minutes its in the red and water starts comming out over the overflow as the system is very presurised, the water hoses are also extremly hot and solid to the touch.

My garage has changed water pump, thermostat and radiator, also flushed the system etc to no avail ?

So here is the problem, he has been advised that there is a common problem on these engines where they can crack in the BLOCK causing these overheating problems. So if you go to the expense of changing the head gasket etc, you can still end up with a problem ?

Is this true, are there any checks that can be done etc ?

Thanks in advance for any help or advise.

I'm afraid you have all the classic signs of a blown head gasket or cracked head.
Unfortunately with the BMW engine overheating often leads to a cracked head. You should do a search under p38 diesel overheating. check out threads by Geekfreak and Wills. They both have been down this road. In my own case I ended up replacing the block, head, water pump, thermostat and radiator, but mine was a worst case scenario where the head had lifted with aprevious owner and the repair helicoils pulled under my ownership.
The general consensus is that you should replace the head, pump and rad once you have cracked the head or blown a head gasket. Use genuine pump and rad.
Sorry for the bad news but it is the one real weakness of the diesel P38