Have a strange problem, well maybe not strange but odd. As soon as she starts heating up from cold its as if she is not catching a gear right and the revs just climb up, very quickly she then starts to overheat. On inspection I have found traces of coolant around the engine bay. When I have looked at the coolant bottle it has filled right up and then drains out as she cools with a gurgle and need to top up. Suspect it might be the water pump but the not catching gear and high revs as the first symptom have me worried it might be autobox related. Any advice much appreciated. RRFF 2007

Have you checked the oil dipstick for signs of emolsification(SP)?
With the collent header tank being full and then draining, it sounds like it's being pressurised which could indicate a head gasket.

Not clue with high revs & failure to change up though.
Does it do this on it's own, without any throttle input from you?
What happens when you take your foot off the throttle?
It sounds like the kickdown is in operation so could be ECU or throttle peddle related.

Any faults/lights showing on the dash? 

Checked oil, all clear with no signs of emulsification at all. The revs are odd, it sounds as if it is revving while not in gear but I am still getting some drive although reduced, foot of the throttle it drops revs as normal. No fault lights but as mentioned starts to overheat quickly. RRFF 2007

Well as it's obviously a she, maybe it's "that time"?  Got - 2017 SDV8 Autobiography in Loire Blue
Had- 2008 TDV8 Vogue SE in Java black
Had - 2007 S/C in Stornoway Grey

Check the gearbox oil for signs of emulsification or water in the oil.

Not heard this happening on a rangie, but on some cars a common failure mode is the gearbox oil pipes that go through the radiator (to control the temp of the gearbox oil) become perforated and the pressurised water ends up in the gearbox.

When you top up the cooling system, do you remove the bleed screw on the header tank and how much water does it normally take to fill it?
It could just need "burping" (have air trapped in the system somewhere).