Ok...read your replies.

With regards to the A/C pressure i have tried with and without the A/C on and it makes no difference.

The car has power but not the same as before, it is also taking longer to change gears (its automatic).

I also cannot hear the turbos as before..It is indeed a diesel. I will check the reservoir is connected properly as suggested.

It is indeed a diesel so this could be it. I will check and report back asap.

Thanks for your help so far.