There is a race to the bottom when it comes to wages. JIB wages are reasonable its finding JIB companies that is the hard bit. 30-40 years ago usually easy to find but not so easy now. The companies that use plumbers large scale, have all kinds of ways to employ them now. Agencies, sub contract, short contract, bonus, price work and all kinds. Sometimes even the ones that pay decent money, the plumbers daily job load is fantastic. The likes of the companies that do mostly HA work pay in all different ways and seem to try to reduce wages as much as possible. One company gets all the fast trackers that companies will not employ and pays them little or a reasonable amount with a big work load. And they want you to be multi skilled. The thing is, you might not like it but they get the guys to do it.
A mate was telling me about his mate some years ago that went and got a job with a big national company, it was a good deal money wise. But the work and driving to and from places meant he was out at about 6.30am and not getting home until 11.30pm every day including weekends.