First to say 42's have never really been that popular here in the UK, hence why Bach don't even try to sell here now
Value depends on age and condition is it a gold bell or yellow, have seen them sell anywhere from £400 to 695 maybe a bit more depends how fast you want to sel it
2nd tenor, Bach mouthpieces have changed over time NY are the original larger sizes are very rare, mt vernon are different cup and rim shapes and seen by many as the Bach mouthpiece especially the 11c and rarer 6 1/2 which go for big money
Then came the first Corp they again differ in design of...
IMHO as your new to the area, go play with every band you can, that way people get to know you and your playing abilities, also you may then get invites to play with other ensembles beyond brass banding.
Let’s say that most if not all Patrick’s students would have played a 24 aw as for the 18 well that used to be popular with BBb players, certainly in the forces bands
If the Wick 3 works for you then use it, they were developed with Stephen Wick Denis’s son who was a fine pro player before...