“I’d assume a salary will be about half your day rate…“
This. Based on many years working in finance supporting white-collar engineering, contractors’ hourly rates tended to be about double the raw rate for an employee (which was salary / 2080h).
“Personally I would see job security in a permament role as a bit of a fake benefit in that I don’t think it really exists these days.“
This. I was with the aforementioned engineering company for ten years. When the work slowed up I was made redundant. The only “security” comes from the hope that giving you some redundancy is a slight disincentive to getting rid of you. It was only statutory redundancy and equated to less than 2% of the total pay I’d received in those ten years. Bugger-all really. I would have been waaaay better off as a contractor for those ten years.
“Your day rate is about 150/160 at a guess?“
You don’t live in the south at a guess 😀 The last few tradespeople I’ve dealt with have been £300-£500 per day.