In case anyone's interested...
My Daytona Roadstar GTXs are about 10-12 years old now, and they've been brilliant, but the soles have finally given up the ghost, though not the waterproofness!
I've had them re-soled by
Sport & Leisure Boot Repairs and am very pleased with the result.
http://sportandleisurerepairs.com/collections/motorcycle
In total, it cost £56.95, and for that, they send you a bag, you phone them when you're ready, and then a courier comes and collects... in my case, within 2-hours! They collected on Thursday, and I got them back today (Tuesday).. and here are the before & after pictures...