Reassement of mortgage amount when moving house

Hi all

Newbie here, please go gentle on me :beer:

We have a pretty good mortgage product (that we'd like to keep) and we're looking to move house. Since we took out the mortgage our circumstances have changed quite a lot, I was wondering if our mortgage company would reassess the lending amount (asking for our current household incomes etc) if we moved house and stayed with them for the mortgage?

As we have less income I don't want to contact them to ask just yet!