In reply to Ridge:
So your options are :-
45 - can't add the OS Grid Ref
245 - was it just a bad manufacturing batch, and fixed now ?
645 - would fit the bill
735 - slightly older generation triathlon watch, but a solid reliable performer
935/945 - too expensive
Instinct - might fit the bill, a bit "old school, ie Casio" looking, but good reviews
Vivoactive 4 - touchscreen, uuurrrggghhh..........