Can thoroughly recommend the site mapkiosk.com for anyone thinking of getting new OS maps. They are very reasonably priced, come with free postage and are despatched the same day. Brilliant.
I've just discovered that if you go onto the ordnance survey's own site (google it) you can put in a post code and or grid ref
and it will show you a small section of a landranger map with that ref in the centre. It's just enough to see if a new site is next to a nice river,woods, footpaths etc. or within a few yards of the fastest loudest dual carriageway in the New Forest... for example! We all learn by our mistakes I suppose.
Yes, that's exactly what I do, then once I know the number of the map, I order it from mapkiosk, which is much cheaper.
We've just ordered three maps from them on-line and they were with us within 24hrs, which is great because we're hooked-up ready for an early start tomorrow, for a weeks caravanning and we'll be using them.
We usually use the OS website. They often have special offers (eg 3 for 2) and we have also had maps centered on a particular grid reference printed to avoid carrying more maps than absolutely necessary on long walking or cycling events.