I use OS Getamap http://www.getamap.ordnancesurveyleisure.co.uk/ £20 per year subscription, covers the whole UK up to 1:25000
But I've only used it for personal use and I notice there's no option so save maps as an image which is what the example you gave is; however you can print maps and I suspect with a pdf print driver you may be able save the resulting pdf for download from the web by your users...don't know if that could be an option for you