Thanks LuposO 1 and Stevie. I have got them working now (I think as I haven't yet road tested them).
The problem was that, in my ignorance of these things computer, I had copied the ov2bmp FOLDER to Gt Britain maps. Apparently I should open the folder and then copy the individual files. When I did this the new POI's appeared in Tomtom. I have enabled them and applied sound warnings so - here's hoping.
A useful link to explain all this is:
http://www.pocketgpsworld.com/module...wtopic&t=21790
Thanks again for your patience and help.
Pastor Dave