Thanks for all the suggestions!

I'm surprised to see Phuket written off. I thought there were nice spots?

Langkawi: I've actually been over 20 years ago (stayed at the Berjaya). Would love to stay at Datai but that's well outside my budget, unfortunately.

Pulau Tioman sounds intriguing. Any recommendations for decent mid priced resorts?

And Kota Kinabalu got me thinking that I could actually mix a bit of other activities around Sabah.

Desaru also had come up on a search but it looks like the area might be somewhat uninteresting.

Am nowhere nearer to a decision, but got plenty for a deep dive!