Don’t despair. Ask the chemist for a pill cutter and cut the 20mg tablets in half. How many are they prescribing - 4 per month? If so, take half a tablet every 3-4 days. If they are prescribing 8 per month, cut them in half and take every 2 days. Research data suggests that this is nearly as good as 2.5mg / 5mg daily.
I would still complain to the CCG though.
Is the psycho-therapist your area’s version of an ED nurse?