Electrical advice trip switch

[bodgit]

This morning about 6.30 I had the downstairs lights on in the kitchen as I went out I turned them off then back in again about 5 mins later. All the downstairs lights went off except the one in the garage. I checked the box but no switch has been tripped. I changed the complete light fitting and put in new bulbs but still no lights. Had all the switches off and checked for power but nothing going in to any of them despite the trip switch still being in the on positions.
The box was new one year ago today and the house is 22 years old so wiring should be ok.
The electrician who did the job for me hasn't called back yet as he is working in Liverpool. Any ideas as to what to look for.