If SU booked the connection as one ticket, then the misconnect is SU's responsibility. However, that is not clear from the OP. "Reservations code", PNR and the like are irrelevant. What matters is the e-ticket number. If this is one single ticket LHR-Ufa, then it is SU's responsibility. If there were multiple tickets booked into one PNR, then it is your problem.

There are several approaches:

1. Depending on the delay at Ufa, you may be entitled to EC 261/2004 compensation as that is measured at UFA, not a conection point. The fact that the aircraft may have touched down 1 minute late is irrelevant.

2. You may have customer rights through the credit card used, all depending on the country of its issue.

3. Your travel insurance may cover this.

4. If you have a UK address, you could start an MCOL action against SU.