Disco 2 Dumping Water

Hi Folks help needed is it the end of the road for my V8
So had to top up water after every journey at weekends as doesn't move during the week no puddles under car after parking! today the temp gauge went off the scale waited until it cooled down refilled system started the car without cap on reservoir and let it tick over until the fan ran! however didn't get that far as water was erupting out of the header tank like a volcano! would I be right in thinking that combustion gases are getting into the cooling system? or the water pump isn't turning efficiently enough? if that's possible? or both!!
Many Thanks in anticipation

likely head gasket or cracked block behind a liner, when running again check rad gets hot all over, all hoses do to and return pipe to header tank has a good flow that would show system is ok

Sounds like it. I have had this fault before and the overheating & topping up became almost a daily thing and I was carrying gallons of water with me in the boot "just in case".
I had the local indie do a pressure-test on the cooling system and it came out fine and they could find no leaks and no reason for the overheats and water dumping.
Oil was clean and clear and no "mayo" present anywhere.
In the end I lost all hope of getting a proper diagnosis and chucked a shot of "bars-leaks" in the system. The radiator was a new one (less than a year old) so I wasn't worried that it would block the radiator.
Instant-fix. No more water dumping or overheating from that moment on. Why? I have no idea. I suspect it could have been a tiny fissure in the block/head that got sealed, but I don't know.
All I do know is that I then did over 60k miles and never had another overheat or coolant-loss problem. Go figure.

Thanks guys I thought that might be the case gonna pop it round to Landy specialist near me to see what he makes of it!! But if a shot of Barrs leaks does the trick then happy days. Be a bit before I can do it but anything is better than a new engine!!!!

UPDATE:- Well been to 2 independent Landy specialists and both have said head gasket, Found some stuff called Steel Seal which actually comes with a warranty that it repairs head gaskets and cracked blocks!! Followed the directions to the letter and the video on youtube 2 bottles later and £91.00 No it didn't work!! MOT due in May with all the new regs on the mot I very much doubt it will pass without very deep pockets so I have no other choice that to off load it, So if anyone wants one 4 spares or repairs open to offers

You have symptom a iffy head gasket a you now know, unfortunately it's not unknown with a V8 overheating, as you describe, being terminal for the engine with it having a slipped cylinder liner/s.