Probably not able to help much. We got in early and paid for a mooring for 6 months or so before we could get to it! (before M8 bridge open)
Grangemouth sea lock is where BW tend to have boats for sale, and I have heard it said that if you buy one there, you get a guaranteed mooring at Grangemouth, and some priority when you want to move. (Which you will, if you want to boat , as 14 locks to get anywhere is a bit of a downer, even if BW(S) operate them!
There does seem to be some movement on the mooring front: there are a couple more boats at Leamington than there were a month ago, although one chap who bought an ex-hire boat has been waiting for a mooring there for months, and meantime has had to occupy a visitor mooring at Edinburgh Quay.
I think it is possible to continuously cruise, although BW(S) discourage this, and won't issue a licence without a mooring.** However, the mooring could be at the sea lock, and 14 days could be spent at Falkirk, Linlithgow, Edinburgh Quay, Harrison Park, Ratho, etc. (Falkirk and Linlithgow have good train services to Edinburgh, although the train stations are a mile or so from the moorings at Falkirk)
Iain
** But BW(S) licence plus mooring is still a lot less than BW licence