I have more or less decided to buy a Hakko FX-888 as an intermediate solution for the following reasons.
1/ Easy straightforward purchase from 1 supplier.
2/ Quality of the product and the information on the Hakko website (including informative video's on tip use).
3/ An adequate supply of bits that are easy to understand and use.
4/ Small footprint.
5/ High power and variable temperature with adequate heat up speed.
6/ Reasonable cost.
My issues with the Metcal brand are.
1/ The most affordable Metcal machines have been discontinued and can only be bought secondhand.
2/ The PS series uses a lower frequency (470KHz) RF current than the higher end models. They have compromised the design in my view.
3/ Not enough power for my liking.
4/ I do not need super fast heat up times as I dont work in production.
5/ The bits are too expensive AND DIFFICULT TO GET HOLD OF.
6/ I don't understand how the bits work.
Used Metcal units,bits etc are scattered all over the world on EBay and the postage costs add up to more than a new Hakko. When I'm more solvent I may experiment with a Metcal. However my favourite tool so far is the PACE mbt-350 http://www.blackandco.com/govtsales/pace/
which can use 7 handpieces (micro tweezers, hot air pen, vacuum desoldering tool, universal soldering iron, TD-100 iron with tip heater cartridges) in one compact square unit that can be stacked. It has 3 independent channels that can all be used at the same time. Problem is it costs nearly £1k. I think the Hakko FX-888 will do me for now.
P.S Unless I change my mind and buy a Pace ST30 unit with a PS-90 iron. The good thing about pace is that the same iron used on the cheaper units will also work on the more expensive models so the handpieces only have to be bought once. I have also used pace tools before.