Vo2 is stuck on same Amt for months yet have been running on average 25km a week. Why has it not moved?

Try factory reset the watch.
I have the opposite. I have allergy at the end of summer, which means I can't breath normal, so I expect my VO2max goes down, but it remained the same, on 51. Now that my allergy is over, it dropped to 47 :D

Could the reason be that you're running only easy pace runs and the same distance? I have moved up 7 VO2 points the last 6 weeks, and each week I have sessions with  hill runs, intervals and a 10k run, as well as a 20 km long run every other week. 

It's pretty normal if you have it updated after every run in Garmin Connect app. According to my observations, Garmin shows some moving average value of VO2Max, smoothing out the fluctuations between the runs. Check your runs using the online services that provide VO2Max measurement on the basis of every run (like Runalyze, for example). It could be the case that your VO2Max just moves back and forth 2-5 points from run to run, and Garmin just averages these movements. 

Thanks for coming back to me. I will certainly give it to the factory reset and see how that works. 

I’ve been running different distances 5km / 7km / 9km and at different paces. Included in that were a couple of hills too. Maybe I am just that unfit but would expect something to increase. Thanks again for coming back to me all the same. I’ll push the training now and see does it change post a reset maybe. 

Thanks it could be similar to the above re change of pace and distance maybe. I’ll push a couple of harder sessions and ensure it can’t average out at the current Amt. thanks again guys. 

just a note on my V02 points.. I started an intermediate Garmin 10k training plan, and for the first 4 weeks i gained just a single point. The last four weeks I have gone up six. How long have you been doing your workouts?

Usually it's the opposite. You have the fastest pace of improvement when you are unfit, and your VO2Max goes up considerably. It then flattens out when you plateau closer to your peak form. 

Compare your similar workouts on your own. Have your fitness improved? It's easy to check by matching your pace vs. HR. This simple relationship is behind the calculation of VO2Max.