Thanks for your reply.
The shortfall has been paid by myself and my ex partner at different times over the last few years - currently at around £20 a month.
We do discuss this and things are amicable between us having both remarried and moved on with our lives except for this issue which ties us financially.
When we split up she stayed in the property and I paid toward the mortgage until the point when she realised that she would be in a better financial situation to move into rented property and receive financial support/benefits towards this. She dropped t