Can anyone recommend an inexpensive reliable tablet on which to run Skydemon which I'm looking to use in favour of my existing Garmin?

By inexpensive I assume you mean Android?
There are some posts on this site regarding various models of tablets that work well or not quite so well.‌
Generally speaking I would suggest that any modern Android tablet will work okay.
Tony‌‌

Thanks Tony. Yes, correct assumption, I did mean android. I was keen to opt for a good model given that there are a few comments on the site about unsatisfactory models and I thought a bit of research among current users would be useful. Again, thanks.