Richard,
Here is the address of Chris Filnt's homepage
http://www.scatesconcertinas.com/

and this is the article on "Actions"
http://www.scatesconcertinas.com/pdf/RE%20ACTIONS%20-%20thinking%20inside%20the%20box%201.pdf

Hopefully with permission and compliments from Chris...:-)

Yes I agree , there certainly are some advantages with a detachable lever and as I said before ...disregarding the technically theoretical superiority of a stable lever/hook connection I doubt that it means a lot for playing standard. BUT as you can see in Chris´s article there are variants with a forked lever AND a stable axle but the parts still being detachable. Maybe one of those would make the ultimate type?? BUT this will not help YOU Richard in this distress getting the parts in place either.
I mostly loosen the pad from the lever in cases like yours, put the button onto the lever, replace and fix the pad again.

Now to the issue of buttom pressure which is another intriguing one with concertinas! The radial and individual lever arrangement is not particularly suited to get the best working mechanism at all. I have suggested several times that for anglos the German type of mechanism layout ( one common axle for all buttons in the same row and the reeds arranged in straight alignment ) makes more sense than the radial variant. This works splendidly for 20 key instruemnts but with 3 or 4 rows the "Chemnitzer" basical construction with reed blocks may be necessary to get things in order.

As a matter of fact button pressure is often quite uneven with many concertinas and players often seem to be unaware of how important it still may be having trimmed button pressures. It IS quite tricky however to set it evenly. You have to use a proper balance and all you can do with the springs is some gymnastics to alter the pre-tension. IF you take your time setting the pressure evenly you will however experience much improved tonal control. With a piano even amateur players use to be quite sensitive to improper "weighing" of the keys.
Talking about superstition with concertinas...there often is talk about lowering the button pressure to "play faster". This of course is a complete misunderstanding. The higher pressure you can manage the faster you may play of course but there is an individual limit naturally and touch dyscomfort from hitting the buttons may become an obstacle.Higher pressure than 100gram is seldom recommendable I think and with many models pads start to leak if getting down to 40 or less.
Some models are more sensitive to low pressure, particularly those with much varying pad sizes where the lower notes start to leak with energetic pumping.
I started a thread on Button size a couple of years ago - this issue is always important IF speaking about button pressure. Not least since there is an enormous difference in playing comfort between 5mm concertina buttons and say 12mm ones as they are on my Hohner melodeon which got a button pressure of over 200gram compared to most concertinas ca 50gram.