[Dorchester]

Well the missus is rather chilly this morning because she can't open her boot...
I'd told her many times not to slam the boot with too much energy...
Something's broken inside the lock: I can turn the key but when pushing on the button there's no resistance.
What can I do?
I can't raise the shelf except if I break something and the seats are locked in place.
Thank you for your kind and wise suggestions.

[Montegoman]

You should be able to slide your hand or a claw hammer down the back of the parcel shelf, between the parcel shelf and seat back, and release the folding rear seat.

[Dorchester]

Thank you.
But by chance and miraculously I've been able to lift up the tailgate I don't know how because when I push on the button now nothing's moving in the lock at first sight.
Hence I've taken off the shelf, pulled down the seats, taken off the negative of the boot lamp, blocked the closure of the tailgate (if not next time it'll be impossible to redo the 'trick') and tomorrow morning with fresher temperatures I'll take off the black interior trim and have a very close look on how to repair the damage (both screws already taken off, the clips still to pull up).
I'll keep you posted.

[Dorchester]

I've just taken off the whole mechanism in the morning.
Nothing broken, just a bit stiff, need pushing frankly to close the tailgate.
Maybe the heat outside helping the metal to expand...
I've blown graphite powder on every moving bit.
Tried several times. All is OK. Just a bit tough to close for my better half (it's the missus' daily). But it's the first time she has difficulties to open it since nearly 8 years!
I told her not to slam the tailgate but holding it back then when it's put down frankly pushing on it in the end.

BTW I do not understand the use of the key in the button: if I try to open the tailgate with a key when the car is locked, the alarm yells!
So that the key looks useless to open the tailgate... and never I've used the key to lock the boot (and I guess the whole car).

[Montegoman]

The early base models didn't have central locking, so you would need a key to unlock the boot.

[g259fsg]

If it's hard to get the boot to close, it could maybe require a bit of adjustment. There should be a way of moving one or other of the locking parts. I've found over the years, that the constant closing of the boot lid with a bit of force does cause the parts to move very slightly, on my car the lock swivelled slightly as well making the closure harder. As you say, high temperatures could make the problem worse as everything expands.

[Paul_1978_yorks]

It sounds like the boot latch is failing. To be honest I’d just swap it out.

[Dorchester]

It sounds like the boot latch is failing. To be honest I’d just swap it out.

Not a bad idea but swapping for what?
It would be useless to buy an old used one and I can't find any NOS one...