Quote manipulation has really come into focus for a number of big Motor players over the last couple of years. I've attended a couple of really good presentations on it, and the methods of tracking it are only becoming more advanced.
In cases like the one in the OP where it was a completely innocent 'what if' check you'll get a phone call to discuss to make sure you're not deliberately misleading the insurer for a cheaper price, the advisor will be satisfied and that will be the end of it.
I updated the OP about the extras I had to pay. Do you know anything about this 'out of the UK for 6 months+ counts as not being a resident for that time?