Migrating to UC problems

Yamor

There are cartainly rules (contained in Part 4 of The Universal Credit (Transitional Provisons) Regulations 2014). See here:
https://www.legislation.gov.uk/uksi/2014/1230/part/4
See also the ADM guidance here:
https://assets.publishing.service.gov.uk/media/656083bf3d7741000d420157/admm7.pdf

The issue is that DWP are not following the regs fully, or at least their interpretation of the regs is different to the understanding of most advisers, and it is not completely clear what precisely they are doing in certain circumstances.
However, on the specific issue relevant here, DWP have confirmed how they should be doing it in practice, which is that they would take details of the spousal maintenance into account when calculating the transitional element.
Of course that doesn't guarantee that they will do it correctly in your case, but it does mean that if you persevere, you should eventually get what you are entitled to!