You can get Horse Rug Repair Kits which will save a good deal of money. They come from Stormsure Ltd and you can find them on http://stormsure.co.uk/default/horse-rug-repair-kit.html
Yes I have made many successful repairs to various wellies including Aigle, Le Chameau, Barbour and most of all: Hunters.
I use Stormsure Flexible Repair Adhesive every time. I have repaired cuts similar to that shown in your image. I have also fixed puncture holes in soles caused by standing...