Many thanks Bruce and Vince,
Mentioned I had had the problem before but forgot to note what it was.
Cust said he wasn't getting DVB so I naturally expected an issue, and when signal occurred only with the menu, I suspected it was a fault, especially as VHS and DVD worked normally.
Eventually thought to check output on HDMI and found it was there all the time, menu or not.
Penny then dropped - Set I was using was previously used with HDMI input, so menu, VCR and DVD forced set to go Scart, where it flipped back to HDMI afterwards with 'No Signal' displayed.
Made a note this time - Thanks again - Chris.