What Lego to buy my husband for his birthday?

My husband often fondly recalls his great enjoyment playing with Lego when he was a kid. He had a good collection of pieces and would happily spend hours designing and constructing buildings of various styles.

He's not sure what eventually happened to his old Lego, but I think he would appreciate a new set for his 55th birthday in a few weeks' time.

Can anyone recommend a good Lego set that would be suitable for someone who hasn't dabbled with the hobby for a few decades? I'm looking to spend up to around £100. Is Amazon UK a decent source, or is there another online supplier I should consider instead?

Thanks in advance for any assistance you can offer