more earth problems

Well i got up early to to go to Tredegar Vintage car show got the car out . loaded the car up with everything set off mile down the road misfire started here we go looked at the clocks no fuel gauge,volt meter,temp but car still running pulled over and it stopped no electrics what so ever , Then all come back on so i set off again mile down the road all went off again , So i thinking must be a fault with the ignition switch took ignition switch out on the side off the road could not see any thing wrong other then one lose wire. Put back in ,all well down the road a few miles all off again so it was hand up in the dash give the wires a wiggle nothing .Pulled the heater up every thing back on so me thinking must be a lose wire above the heater so i did get back home , A few hours later and a stiff neck heater out. I could not see any lose wires (heater going back in another day) . So every thing working again i set off again down the road lost all electrics again this time i was going down a hill so pulled into the side when i put the handbrake on everything worked i could hear the fuel pump running take the hand brake off lost everything pull it up all worked again so drove home with the hand brake on a few click all ok So all i can think was it had to be losing the earth So cleaned all the earth leads going to the chassis ran a extra one to the clocks , Been out down lots of bumpy roads and all is fine so that was six hours in total. Don't we just love our kit cars