Andib thanks for all the feed back.
Andib: I was using SP3 in my University lectures with 250-300 Students in a room all with smart phones / laptops running causing noise and I've never had any issues with my pen not being responsive. Maybe someone has damaged the pen in store?.
I've never had to re-pair my pen in the life of owning the surface (6 months) with the exception when I clean installed my surface with Windows 10
I suspect that the BT issue I was seeing was that the area had so many wifi APs broadcasting. You wouldn't typically have 300 devices in a lecture theater set up as APs and all broadcasting their existence.
Folk would typically set the BT on their phone not to announce it self. I know that's how I run my phone anyway.
The problem in the department store is that they just seem to have truck loads of stuff that's all broadcasting it's existence. When we attempted to pair, the SP3 found at least 20 devices, this for a technology that's only meant to have a 10m range.
I have to point out, that once we got the pen paired it was faultless and extremely impressive.
Now I'm wondering about Windows 10. How far way is it? What will the upgrade be like? Should I just wait until the Windows 10 SP version hits the shelves?
I confess I'm now thinking about my urgency.
D