How weird I've just been looking into this as my dd is tortoise mad. My initial Internet search suggests it's a Bloody Pain In the Arse and I've shelved the idea. I'll watch this thread with interest though.
Be aware they should live a very, very long time. Never had a tortoise but visited a tortoise sanctuary on holiday once. Whilst there DD1 held a six year old tortoise that was still the size of her hand. So long time before they are full grown.
Also sadly many residents were blind because before they had been rescued their shells had been varnished
No help whatsoever but I've just had a browse through Gumtree and it seems that with reptiles (as with guinea-pigs) there is someone out there (well several people) who want to pass on their unwanted animal -maybe they didn't do the research- and make a few £££. Of course there are some legitimate sellers/breeders out there.
In Turkey we stopped at a cafe resturant. They had a garden with a low wall surrounding and dozens of tortoises wandering round, quite quickly some of them . It was lovely to watch them. Some huge, some the size of a lemon.
I met a man in the queue in the supermarket who was inheriting his Grandmothers tortoise. He was very pleased with his inheritence, and the tortoise was a good age. Something to consider