Eventually got the A/C sorted. Would you believe there are two fans, one to cool and exhaust the heat and one to blow into the caravan. I had the cables fitted to the repaired PCB the wrong way round!
I didn't realise because the plugs and cable colours are the same so when checking against the image I took, nothing looked wrong. Now I've swapped them over the A/C works as it should. Yay!
I did manage to sell the new PCB on the Bay of e after a couple of months for what I paid for it less their costs. Not bad in the end. Sometimes my need to do it myself isn't cheaper/better but stuff is experienced so there is some value. Having had no income for the last 6 months forced my hand somewhat. Alls well that ends well I suppose.
I've just returned from 5 weeks of touring Dorset, Devon and then up to my Daughters to look at our Grandson from a distance and the A/C worked well during the hot spell.
What didn't was a leak from the roof vent above me in bed at 2:00am. Again the cost to get this sorted by Vanmaster is nil but about £350 for fuel and overnight/meal, it is way over the £10 of sealant (Sika flex) to do it myself. So another job done by me and done at a very reasonable cost comparatively.