First of all, let me tell you it's very hard to find the engine but still let me know which variant is this? TD4 diesel 2.2?
I recently swapped a tdv6 2.7 diesel v6 luckily got one clean engine in Islamabad. Overhaul also was an option but the waiting time in importing parts and total etd was around 1-2 months so the customer opted for a quick solution. So I think it would be better if you go for a overhaul or fix the issue, because it's not confirmed without testing that the engine gasket will be gone, there are plenty of other reasons for the heatup too. We are very well versed in range rovers.. Did complete revamping of two 2006 recently three weeks ago , one was diesel which I mentioned other was v8 supercharged 4.4L. So if you are okay with time and want to rectify the issue, we are in Islamabad