You "Might" get 3.4A a minute a year if you watch closely when everything is 100% perfect. :-)
If the cells work as rated, then 3.4A is good for figuring how much power they can make in a day, on a fixed mount at the proper angles. Take 3.4A X you areas solar insolation hours for the time of year.
So if your solar insolation for now is 4.5 Hours, the panels should make 3.4A X 4.5H = 15.3A-H per day, into a battery.
That is for 36 cells per string, no extreme wire losses, etc.
It works out quite well.
England's average worst case winter month is about 1 hour!
Wow! Thats nearly as bad as here, often listed as <0.5H.
I can not find 12 month charts for England.
But its better than that 11 months a year.
Can't help with the loose connections, etc.
Tried DIY a time or 2, it didn't turn out well, I gave up. :/
G-