Hey JStancombe
Just wanted to let you know that you are definitely not the only one this happens to
The way I understand it is that initially the muscles in your hands are stronger than the tendons that support them, so even though you are able to climb, the ache that you are feeling is actually less of a muscular ache and more of a ligament\tendon ache. It is always a good plan when getting back into the climbing to do a little and really easy often, as opposed to a lot less often. This allows your ligaments and tendons to strengthen without putting too much strain on them. It save injury and discomfort. Also, climb ridiculously easy routes for a while until you are feeling comfortable.
Hope this helps
Oscar