I have a Charles Lancaster Beesley built BLE Self opener. It is one of Toby Barclay's Heritage Guns. My SN is 07408 (#2 of pair if someone has 07407). It is from 1894.
Toby included a correspondence from 8/21/2004 to:

Mrs M. Mitchell
19 Portman Crescent
South Bourne, Bournmouth
BH5 2ER
Tel 01202 432950

She had (or still has) Lancaster records covering: (per the note)

Guns 5449 to 11949
Pistols and Rook rifles 7000-9417

Mrs Mitchell wrote the entry information by hand. She did not at the time have a means to copy the page.

Maybe Lagopus could make a UK call to check on his guns to confirm?

Good Luck,

Joe