2007 1.4 Climate - A/C not working(ish)

[M60NJP]

Appreciate any pointers please for the following issue:

System has just been regassed. Both pre- and post- regas the a/c has been only 'partially' working. It would work briefly (blow chilled air) and then slowly increase in temperature until the air was the same as the ambient temperature. The a/c compressor would engage/spin but only for a matter of seconds and then stop, then restart for a few seconds after a few seconds etc etc.

As the air is occasionally cold, I'm assuming the system is correctly gassed and the compressor works (latter might be an assumption too far?). Changing the digital temperature on the dash makes zero difference when needing cold air, but seems to work in that it allows warm/hot air from the heat exchanger when needed.

So - is it the compressor on its way out or is there a common electrical fault which is 'pulsing' the compressor for only a few seconds and then telling it to stop......or something else completely??!!

Thanks in advance