360GLT Electrics

[kev240]

Can anyone out there please help me with an electrical problem which has occured on my 360GLT, 1989, 'F' reg.
returning home last night,every time I touched the brake pedal, my lights, main/dip beams and instrument panel lights all flickered.
When I got home and switched off the car it refused to start, the ignition system appeared to be 'dead', and the voltmeter instrument was not registering any voltage.
After checking/cleaning the more basic items,(battery leads,starter leads, alternator leads/plug etc),there was voltage at the positive lead to the starter which illuminated my test bulb brightly,I consulted the Haynes Manual and the 'Fault Diagnosis'(Electrical) Section, the most apt explanation in my thinking was listed as 'Battery Will Not Hold Charge' and the cause would appear to be 'Short circuit in lighting circuit causing continual battery drain' I came to this conclusion due to the flickering lights.
So far i have carried out the following:
Changed the brake light fuse, bulbs and even the bulb holders, checked out the rear light earthing, and all the other basics checks mentioned earlier.
The car is easily started,(first turn), from a jump start or short downhill bump start, the voltmeter immediately rises to its normal position, but after a run of up to five miles without using electrics the car refuses to start again. Once restarted the car idles normally and all other electrical equipment appears to be working normally apart from the flickering lights when the brake pedal is touched.
Can anyone please provide me with ideas/items to be checked.
Sorry this is so long winded.
Kevin Devine