DRLs stopped working (Fault Gone Away)

I had a service/MOT done by a local garage and noticed a couple of days later that the DRLs were no longer working. They do light up when I lock/unlock but as soon as the ignition is on they go out.

Not sure if it is something which happened during the work as I cannot say 100% they worked when I dropped it off and not when I picked it up although I am fairly confident. Is this a common issue with a simple fix?

Grrr I hate when that happens. Fault appears out of nowhere then one morning it goes away again for no reason.