TURBO R ELECTRICS DEAD, NO IGNTION, ALARM STILL CHIPRS

[djgarfield]

Please can any one advise me.. My 1996 late chassis SZ Turbo R has lost all electrics. it started off with the starter only cranking a couple of times then only one crank, then only alarm and central locking working, then finally only central locking and then nothing... like as if the battery was going flat.
the car seems like it may be immobilized in some way?
I have taken the CDL alarm module (under 2nd dash roll top)
and changed batteries in the module which has bought the alarm arm/disarms chirp back but stull nothing else work (no ignition lights at all)
The main battery has also been checked and it is fine!
Any help or advice would be very much appreciated.

[djgarfield]

Thank you so much for the reply.
You are my hero as you were totally correct on the isolator battery switch being the fault. I did consider that but thought it looked ok, but you motivated me to do it anyway and
I now have full ignition and electrics working,
however I still do not have a start/crank.
I am having trouble locating the starter and its related ground lead!!
please can you adviser how/where I can find this and any other suggestions would be greatly appreciated.
I feel we are so nearly there! I will await you reply
PS I have checked and swapped around the ignition and starter relays and checked the fuses,

[djgarfield]

Thank you for the pieces of advice, much appreciated. The starter strap seems ok, though I have found that the car will now start but only with the ignition turned on (as usual-but the key does nothing in the start position) and a 12v prompt directly into the wiring loom plug in the passenger footwell/behind the glove box. The key will allow the engine to cut as usual. I will investigate to see if it can be connected back to the key otherwise I may consider running a starter button and 12v with it to get around the issue..