Managed to get the multimeter out on the weekend. We had a circuit conection from the GPS wire to the lowrance head unit on all wires but noticed there was also a small 2nd resistance on one of the other wires which indicated a possible break.
I cut the antenna and moved it to the head unit where I reconnected it. It immediately showed all satelites as per test using Petes antenna.
It failed to get a lock so I tried the soft start that you described and it worked like a charm!
So now I just need to get a new cable.
Just wanted to say thanks for both of your help.
I thought I was home free, but now it is not picking up the map data and will not zoom any further than looking at the whole UK which indicates to me that it is not reading the card. Is this just a bad connection? I have tried WD40 and cleaning the contacts but to no avail...any ideas?