We're registered installers for sure stop, not that it means much!
Surestop are great products for the elderly to operate which is mainly why we sell them, also good for inaccessible stop cocks. I always leave the old stop tap in place though, I'm 99% confident in the product, but that 1% will get me in trouble! The actual stop valve (product codes ending in 'L') is wras approved so can be used alone without a stopcock before it, and it'll work down to zero pressure (as required by wras) unlike the remote isolators (products ending 'M') which will only work down to 0.5 bar.
hope this helps
Dave