A few ideas Rookies programme at Activ Camps (12-14 yrs) The Font bouldering (runs sessions for 12+) All Stars tennis - age groups are 8-12 and then teen, so yours would currently be at the upper end of their group but that would change when they hit 13. Balham Leisure Centre run supervised junior...
I attend Barre classes at Willow on Northcote Rd and would very much recommend. Some instructors/classes are more demanding than others, happy to share my view on which ones via PM!
There are private lessons on a Monday at Balham Leisure Centre from 5pm through to 7pm, though I am not sure if there is still space. There may be other days too. Contact Delene - email is DeleneJonker@pfpleisure.org
I don’t have direct experience but I imagine the school will find it hard to fill the spaces for the summer term only and therefore may be amenable to agreeing a reduced fee for that term (for them it’s better than nothing). I hope you can manage to keep them in till summer.
We used Beatrice at Ma Maison based in Abbeville area to make curtains, blinds, and then hang. We also chose and ordered curtain poles through her. Very happy with the results. I found the fabrics myself but she can help with this if wished.
The Winckelmann tiles are the best replicas. I believe London Mosaic use these. However we got them from Martin Mosaic via his ebay shop and then got a tiler to lay them (you do need someone with experience in Victorian tiling unless just filling in a few gaps).
Do you have empty flowerbeds as cats love these (as they can easily bury their poo)? If so, you could try putting mesh across any bare patches as a temporary fix until they are filled with plants. Some cats are put off by citrus peel so you could try that. Alternatively, a squirt from a water pis...