If you delete an app that you have paid for can you then reinstall it later or do you have to pay again for it? Just asking cos my OH has filled up his phone and needs to make more space temporarily ...

Yes, as long as you log into the same Android account.

Excellent, thank you.

You shouldn't need to though I have heard of problems when transferring apps between phones, not sure about reinstalling to the same phone.

Backup and restore is no doubt fine.

An uninstall and install will certainly vary.

I wanted to add that there are issues doing uninstalls with android as it does not free all the memory it should. Sample thread here,

http://androidforums.com/desire-supp...tc-desire.html

I have apps I paid for 3 years ago on my current phone (4th since I joined Android) and they are also on my tablet and my wifes phone (I added my account on there)
you can uninstall and reinstall as you wish (as long as it's not pulled from the market), when you find the app in the market instead of a price it just says "purchased" (or it will also always be at the bottom your "my apps" list when not installed)

I have never had a problem in my experience of onwing 5 Android phones and now an Android tablet. As I install custom firmware about 40-50 times as well which involves reinstalling all my paid apps I can't see there being any issues.