Solved!
Similar solution to Nadia's worked for me.
I went into the advanced WiFi settings on the TV and changed DNS server to Google's:
8.8.8.8
For some daft reason it was pointing to the same address as the gateway.
I'm sure there is a default DNS server for my ISP that would work also.
I'm no network boffin so maybe someone with the smarts can tell me whit's gahn oan?
Ta,
Wilburforce