Existing leaves won't regenerate if they're turning brown. Its probably just as well they weren't in direct sun for the time you went away, given they weren't receiving any water!

I would wait and see what happens over the next fortnight before deciding to cut back hard - check for signs of new growth during that time, and by then, most of the leaves which are dying should have dropped off. Don't feed it, keep it watered, but not too wet - overwatering won't make those leaves reflate and grow again, so water when the surface of the soil in the pot feels dry to the touch. If you have to cut back, cut back to where there's growth beginning. Hopefully that won't be too near the main stem, or cutting it back very hard might mean lots of shoots from the base.

Thank you for reply, I really appreciate your input Bamboo.

One last question, I was really surprised how quick these plants went down without water, I was under the impression that Olive trees survived very well with little water. 16 days without water does not seem very long, how do they adapt in the hotter countries they originate from?
If I had known I would have asked my daughter to water them for me and will do in future.

In hotter countries they grow in the ground and the roots go down very deeply into the soil. This is where they get a good supply of water from. Of course, you can't do that in a pot.

We have to water them in pots every day in the desert. They would probably need it less often in the UK, but I would still expect it to need it once or twice a week, there.

As bulbaholic says really - if they're in the ground, the roots can venture where they like in search of what they need. Not so trapped in a pot. And you can't rely on the rain watering them either, it doesn't really get into pots much, they need you and your can...

Thanks for all the advice, lesson learned, I will water regularly from now on.
Can anyone please recommend the best feed for my pot grown Olive trees, I have been using Growmore and I think I fed them a nitrate feed earlier in the year. Before this they seemed to be very healthy but not many olives for some reason, i've had them 3 years. I didn't plant them to grow Olives but wonder why not many are produced by the trees.

In warmer regions of the UK, you may get fruits, so like the south or west, but where you are, its not very likely other than in a very hot summer. Information on watering and feeding below; there's an embedded link to what type of feed to use

https://www.rhs.org.uk/advice/profile?PID=138

Thanks you for all your help Bamboo
kind regards Stewart