young Ed
Veteran
save your pennies and get a garmin edge touring or even the 800 you won't regret any penny of it!I have a very old Garmin Etrex which doesn't have a mapping facility. The map is used by my MemoryMap software on my laptop at home. I plot the routes on that and save them as GPX files which I then upload to the GPS. I follow a 'breadcrumb trail' on the GPS screen when out on the road.
That system works really well until there is a change of plan! Usually, all is well, but just a few times in 8 years I have encountered diversions and had to improvise.
I know that you can get OS maps for many GPS devices these days, but I don't have experience of them.

i got the edge touring and love it aside from having the maps etc it is just much more bicycle friendly and with the 800 you have the HRM and cadence

Cheers Ed