I have thought of the side extension but I have hit the ceiling on what the house is worth.
Even if the kids don't live in it, it would be a form of income for them. I may just scrap the idea and buy a small flat to do up but if you don't try these things.
If i could buy the garage, it may work. Devaluing the current house is not an issue, next to the piccadilly line so house prices are silly anyway.
Anyhoo, thank you for all the comments.