I have a fault with my C30 Air conditioning and could really do with some advice.

At the end of last summer the air conditioning stopped working. I didn't bother looking into it until this spring. I put my gauges on the system and the pressure appeared to be low, the static pressure was around 10 psi on both sides. So I got the system recharged at my local garage but it still didn't work. When I put my gauges on, the static pressure was around 50 psi at approx 12 C. With the engine running, air con on max and recirculating, the pump clutch is engaged and turning correctly. However, with my gauges still attached, the pressure on the low side was between 25 and 30 psi but on the high side it was around 100 psi. At this point I decided to get a replacement pump. So I sourced a guaranteed used unit, had the system evacuated and swapped the pump out. I then had the system recharged at a different shop, just in case, but the result is exactly the same, 25-30 psi on the low side and 100 psi on the high side, with no cold flow in the cabin. Any advice would be gratefully appreciated. Thanks.