I'd wait til Christmas, personally.

I've heard that the UK cooresponds to US zones 7 and 8, which means to me that you likely could prune now and depending on how late cooler temperatures arrive, it would likely be fine.

Pruning above buds forces those buds to grow. Cutting below any buds (that lanky area) may force new growth from the roots, which could get you more stems overall. I wouldn't do it below any buds unless I knew the roots were very well established.

~Chills

If your growing zones are like the US zones 7 or 8, I would definitely prune it now before you left if someone is going to be there to take care of it (ie keep it watered and fertilized). Pruning now will cause more growth and more blooms. I have cut stuff back here, both type IIs and IIIs as late as late August and gotten blooms before the first frosts. If noone is going to be there to take care of the plant, I would not prune now and prune it either at Xmas, depending on what the weather conditions are like then, or wait until March.

Wisely is supposedly either a type II or III clematis according to info I got from the Evixon person I emailed to when I first got all 4 of the RHS named varieties. At that time there was no pruning info out there about them, so I contacted the Evison website (someone gave me the web address and I can't remember whom now). I was told Harlow Carr and Rosemoor were definitely type IIIs, Wisley could be treated as either II or III and Hyde Hall was a type II. I however have always treated Wisely as a type III in my garden and I see that COTW has it listed as a type III also.

I agree with the pruning advice chills gave about where to prune it to. If you cut below any visible buds and you haven't planted the plant with dormant nodes below the soil level, the plant may be stressed. The stress could either force new shoots from the crown or it could kill the plant. I wouldn't chance it if it were me!

Thank you so much for your speedy responses. I shall wait to prune until xmas or early march, same as my Rosemoor which is growing nearby. The wisley has given its all for at least 2 months and that is with benign neglect. It would be superb if I could take care of it more consistently

I'm glad I popped in here. My Rosemoor plant tag and COTW says it is a group 2 pruning type. I didn't get many flowers this year, so next year I'll hard prune it.

Hi Joan. Long time no hear. Like anything else, most of the type II clematis can be treated as either type IIs or IIIs depending on your growing zone. My Rosemoor has always been treated as a type III. Let us know how this works on your plant.

Congrats on your marriage since that is what I assume you meant when you sent me your new email address.