I'm inclined to agree with Ted - and go for an Anson & Deeley boxlock.

Both the round action and the best grade SLEs (H&H, Beesley/Purdey) are superb work, but as an all rounder, the A&D is really hard to fault.

Of the Beesley based SLEs, the Henry Atkin 'Spring Opener' version of the Beesley is often considered (including by Gough Thomas) the finest version of that action.