I have just tried several times and given up on plotting a route on OS getamap. Why, because it keeps zooming out and jumping away from where I want to be for no apparent reason. Am I doing something wrong, is the system useless or am I just crap?

I've never used it Ray but you may find it easier to plot routes on bikehike or mapmyride. If it's printable maps you're after, mapmyride is fairly straightforward.
If you want routes to transfer to a gps bikehike is better. You can switch between map types OS etc...

is the system useless

Oh yes ... take Dans advice

Thanks, can't afford GPS and love real maps , will check the sites you mention.

Do people think it a good buy? I have some Memory Map where you buy a download package of so many square km and download bits you want, as you want it. I also have the National Parks. Wondered if I 'need' this or not.

I've used getamap 3 times. I got 3 seperate 1:50,000 A4 map sections for £1 each otherwise I would have had to buy 3 full maps that I probably would never use again so worth it on these occasions.

I find it awful to use on a MAC but fine on a PC.