We see this alot but your friend's workplace IT made a bad choice of LAN addressing and are leaving it to home workers to remidiate 
Because it's entirely foreseeable before deploying remote access VPN to know what default address ranges are commonly used by home and SOHO routers and choose something else for the workplace (out of the 172. or 10. private ranges).
I remember setting up VPN for my office 5 years ago and in addition to drawing up a compatibility / performance chart for licence-free platform-agnostic client protocols, this was basically item 1 on IP numbering considerations.
That said, I have changed the IP range for my parents Sky router and it did take (I think it's Technicolor but older as it only does .b/g/n and not dual band / .ac Wi-Fi).
When Technicolor was Thomson they did have template based configs perhaps it might be overriding things. Or do Sky routers get routinely reset if the ISP pushes out f/w updates or configs for IPTV?.
Hi.
I'm so sorry I have not replied to everyones posts until now. I've been so very busy and have hardly had time to check my emails let alone post on forums. I really appreciate all your posts.
LOL. It was I who set up his router at work. But your bang on right @prizx

I'm no professional and at the time I set it up I was rather inexperienced with VPN. It's a very small business and they don't have an IT support company. But I've managed to do a little networking for them and set up their VPN access which was working really well until I encountered this little problem. xD
Anyway @prizx ... thank you very much for that post. As soon as I saw it I kicked myself... nothing like missing the obvious eh? Im still chuckling now.
@andy88 thank you also. I could have just been a cowboy and changed the IP address on his Sky router but I decided to do the job properly and changed the IP address on the Netgear router at his workplace. Everything works perfectly again now.
Thanks again to all who posted and sorry again for taking so long to get back to you.
Best wishes.
Edited by everway9 (Sat 24-Feb-18 19:22:17)