It wil be difficult to obtain a new mortgage if hew is not working. Hopefully your current lender will offer you a new deal, it's probably worth giving them a call now and asking them.
Alternatively, speak to an independent
mortgage broker and ask what they can do.
As for Martin Lewis's comments, there is no point szearching for a new mortgage 6 months before your current deal expires.
The reason foir this is that the majority of mortgage offers only last for 3 months, so there is no point looking prior to 3 months before your current deal ends.