I don't know what brand of adhesive he used - somebody asked earlier on up the thread, but it's concrete-based by the smell of it. Most of it has come up, but there still a few bits that will be a work in progress until we can get somebody else in. In total, he used almost 7 packs of tiles, a lot of which will be too laborious to scrape free of dried adhesive now. Will probably just buy some replacement packs and give it up as a bad job. Thankfully, we never paid him, so it's been more of an inconvenience than anything else, so I hope the good tilers on here had a chuckle at his handiwork as well as giving me opinions and advice. I wouldn't have attempted this job myself but honestly, I reckon I could have got a straighter line after 10 pints.
Just out of interest, would a tiler, where possible, remove the skirting and tile under door architraves, or is that optional? I'm just wondering what I need to ask for next time.