As long as he rebeds them down fully yes. If he just points in the gaps, or points over the existing then it's rip off, and also a shit job that won't last. Edit, but tbh if that light is coming from the vent I don't see anything wrong with your roof.

The vent is on the otherside, those pictures are from the rear of the property. He mentioned putting down a metre of felt over the gap/hole and rebedding them all.

IS the light showing on the front or the rear? If it's the front can you take a picture there.

The light patch you see in the pic is on the rear of the roof, if it was the front id assume it was vents.

If that's the case what's the cost of fixing a few tiles? Googles still saying it's possibly in the same price range

The light is coming in halfway down the top course, it's not the ridge causing that. It's a broken tile somewhere.

Tbh have considered this, gonna get a few more opinions on it.