25 will have the K series,or newer version thereof.......
There rubbish,very easy to damage the HG on rebuild,or not having it skimmed correctly...my money would be on poorly done repair or done on the cheap,therefore not done properly....
If its loosing water and its not pouring onto the road then i would be pretty confident its HG,either that or when it was done before the head itself has a crack and been put back together with the defect, the new gasket would just split again at the crack....
Probably this was the engine that killed Rover once and for all,
Some Landrover Freelanders had them,hence why you can buy a Freelander today for around £300 to £500! and thats for a 2001/2002 model.... 
The K series is actually a very good engine, despite its age (20yrs since its release this year), but unfortunately under the BMW years, never got the development it needed.
How many 20yr old engines could still meet today's emmissions standard? How many 20yr old engines can still match its main competitors current engines on performance?
Landrover did improve its HG issue massively towards the end of its production - sadly Rover chose not to do this (despite Powertrain - a Rover company - supplied both Rover and Landrover). A HG failure on a Rover K series is guaranteed in the same way as a crank sensor failure is on a GM V6. It WILL happen, just be prepared and try to catch it as early as possible.
With all due respect that quote must be from someone who has never worked in the motor trade, they are rubbish. They will meet any emission standards when they are parked up, broken down and won't run. Absolute rubbish the K series engine in my opinion and experience. A major contributory factor in Rovers decline.
You're entitled to your view, I'm entitled to mine

I made my mind up on not only have owned some, but also having access to the stats on warranties and breakdowns against numbers sold.
And it is fact that the K series can meet the lastest emissions standard, despite being first released 20yrs ago. It is also fact that it is more than a match for similar engines from other manufacturers performance wise, and with the additional bonus of being a very light engine, even when 'wet'.
Rover's (not Austen's) demise can be fairly squarely laid at BMW's door with a disjointed strategy - initially they bought it primarily to gain 2 key pieces of technology (4x4 and mass production techniques - both of which worked out quite well for BMW). Then they decided to try to take a mass market manufacturer upmarket, but using mass market components - ie simply overpricing (a trick carried on by MG Rover, which eventually killed it - not that it was ever viable business, as with no money for new designs, and the Rover designs being taken by BMW before the sale (Mini, and the then new R30 which became the BMW 1 series))
So, no, the engine - which, granted, did need futher development to increase reliability (as Landrover managed to improve, though not entirely fix) - was not Rover's demise.
BMW aside, Rover's other big problem, which stemmed back from the BL days, was Londbridge, and the mentality of the workforce there.