There are currently no maps available anyway near the quality of Ordnance Survey maps. Most maps available locally are so poor as to be dangerous to use off the main roads.
The last issue of maps by Ordnance Survey was in 1973 but they are long out of print. Digital versions are now available and it is possible to buy these on line from the UK in high resolution, full colour, full size. The files are quite large (4 and 5 Mb) but can be printed in parts.