I've seen photos of nurseries using wire horizontally against fences for clematis to climb up.
anyone know what this wire is called & best way to implement this (i.e. How to secure it onto fence) onto my own fence for my Clematis?
I use plastic coated wire which you can get from Garden Centres and DIY stores. The supermarkets also do it very cheaply, but you'll probably not get it till spring now in there. I fix it onto vine eyes which screw into the fence posts. You'll get those in the same place as the wire - maybe not in supermarkets though!
Good garden centres and DIY stores will have vine eyes and tensioners and either silver coloured wire or plastic coated wire.
Vine eyes are simply long, sturdy screws with a loop instead of a head which allows you to pass the wire through so it is held away from the support and allows air to circulate behind the plants. This reduced the risk of problems such as mildew.