Is Adelaide better than Perth? I don't know Perth well, but from what I've seen when I've been I'd say no. It's different (as I think it's different to the UK without being better ...) and while some people find jobs easily enough here in Adelaide, many people struggle to find work regardless of their occupation or how much it's in demand - a trawl through any migration discussion board provides plenty of examples. Building trades seem slow at the moment based on conversations I've had with friends who are in different trades, and as rebates and grants get removed/lowered, and interest rates rise, many are not predicting an early return to boom times.
As for it being cheaper, well, yes, median property prices are lower than Perth's but so are average wages, and SA is the highest taxing state. Property aside, I don't think there's much that's cheap here - food, booze, utilities etc all seem high.
I'd suggest a trip to Adelaide to give you a feel for the place before a decision is made, but if you've already got property in the UK and a support network there, I'd seriously consider making the move back.
PS sorry to heard about your daughter - good luck on that front.