Brake lights on the blink

So I put my '88 Clipper Cabriolet in for its MOT last Saturday. First time since I bought it as a non runner. And surprisingly enough considering its barely done 1000 miles in like 10 years it only failed on a headlight issue and brake lights not working. Then that evening at home before I was going to fit some new rear bulbs I pushed the pedal and they worked?!?!?!
Discovered that when pressing pedal gradually and lightly they don't work but harsher braking and they do?!?!
I think this is some sort of switch problem by the pedal but if anyone knows what this is and how to fix it that would be great!
Got it retesting this Saturday so if I could get the info by Friday that would give me time to sort it out.
Cheers!
Zack

looks like you got lucky lol, mine was a non runner and had sat for years as well, and i had to take off nearly every single electrical contact and earth and clean or replace and 'clart' with copper ease. if you can find the switch on the pedal might be worth doing that, also the bulbs them selves can corrode slightly at the contacts and you'd barely notice, worth cleaning everthing up and squirting with copper ease spray to keep them from drying out. good luck, 

Thanks for that mate! Yeah really shocking lol! Although it hasn't passed yet!! sounds like you had a mare! Is it running now though? Yeah I've loosened up the switch by the pedal a bit and that seems to have done it. I'll have another look in the morning and give it a little spray cheers for the help! 
Zack