Subaru forester overheating?

Subaru forester overheating on every trip

2.0 Petrol - non turbro.

- 1st: Thermostat replaced & chesked (Subaru part)
- 2nd:Filler cap replaced (Subaru part)
- 3rd: Coolant system flushed & bled & correct ratio of coolant added - No air locks or blockages (Subaru addatives)
- 4th: Head gasket replaced (Subaru part)

Information:
The fans work fine and come on at the right time but can't do enough to cool the engine down (it's not the fans!)

Anyone got any idea's because the garage I've been using appear to be clueless!

Thanks.