This is the LEAST optimal time to transplant the clematis. It has just broken dormancy and is actively growing and feeding. 6 weeks isn't necessarily YOUR deadline. My advice; just leave the clematis where it is for now and enjoy it for as long as possible. When the extension is complete (Who really knows how long that will take?) you can reassess the situation. The situation may not be as bad as you envision it to be. Your clematis may be OK after all.

Nevertheless, I think your clematis will survive at least until Fall which is the MOST optimal time to transplant. You can start preparing a new location for it, then transplant it in the fall when it starts to go dormant.

Good advice, but my nosy nature wonders why your cherry tree has to go because of an extension next door? Does it overhang or form part of the boundary??

Agree with Honeysuckle why does the tree have to go? Unless it is in your neighbour's garden there is nothing they can do about it and building an extension that will be right on your boundary isn't acceptable.

Thanks. I'm really not bothered about the cherry tree...it's too close to the house anyway. It's right on the border and needs to come out as it's where they will be digging the foundations and if it's not removed it will be damaged and not balanced properly and it would be growing right up tight against a wall.It looks like the clematis is a goner cos leaving it in situ til autumn isn't an option, but on the bright side. I'll be able to put up a trellis and plant new clematis.

That's true..."When life gives you lemons, make lemonade. lol! Good luck.

Indeed good luck Gaia!

Better double check on the property lines with a surveyor. When time comes to sell your property or visa versa a nightmare might develop. Even if you want to get a mortgage home loan for whatever the reason there will be a title and property search by the lender and if there is a boundary or construction error things can get screwed up terribly. There is still time to get an injunction if there is a boundry incursion in the making. This situation sounds to close for compfort so now is not the time to be so considerate of your neighbors actions when it comes to your property rights.