I first looked into having a switch from the OS mapping into google maps about 6 months ago but couldn’t get it working. Decided to have another go today and it works – yay!

So now there’s two options
OS Openspace
Google maps

For anyone who just likes looking at maps (and who doesn’t?) there’s also an OS maps page with a searchable gazetteer.
I just want to look at maps

And of course, there’s still the ability to upload your own gpx files here