Thanks for the replies so far. I have registered with Remap and will give them a go when I can log in. I will try the magnets but I think they may have the same problem as the Velcro – you have to make sure the two parts of the zip are FULLY engaged and remain there as you pull the fastener up. This seems to be one of the problems – the other being keeping the two sides of the zip aligned as you pull it up. I agree with Neil – once you get it started you can use the fingers and thumb to inch it up fairly easily but it is starting the process which seems to be the problem.
It has to be simple and just as important work easily every time. The string and clip does it but I feel there must be a better solution.
Bob