I think you will find that the only 154's allowed into the UK now are the M series as the older variants were not Stage111/Chapter 111. I always suspected that one or two of the operators of the older models would just add an "M" sticker on the side of the TU-154 sign and keep flying them in and hope we wouldn't notice
(After all tracking down all the varying registrations of the CIS states is tricky as airlines came & went)
If you want to see some fine examples visit somewhere like Sharjah in the UAE, but take some ear defenders. They make a great whistling sound on start up - somewhat akin to the DC-8.