There are lots actually. The one I'll briefly talk about is the 'Sterilisation and Mutilation of Children'.
He's referring to puberty blockers, since it's extremely rare for any gender affirmation surgery to be carried out on anyone in the UK under the age of 18 (perhaps only ever done in relation to intersex conditions that affects genital development).
There are, at the time of writing, no more than 85 kids in the whole of the UK on puberty blockers. That's out of 4.2 million secondary school age children.
I have no idea what difficulties those kids have faced, what difficulties their families have faced, whether self-harm and suicide are serious risks. It's none of my business. It's vanishingly rare (1 in 200,000 children), and if paediatricians can relieve what might be terrible distress by delaying puberty, then who would want to deny this?
Graham Linehan (and other conservatives) present this as happening 'routinely', they twist and conflate facts to push a false narrative. It's appalling.
There are, and have been, thousands of kids currently being prescribed puberty blockers for reasons such as acne, not just for early puberty. None of these people seem to think this is a terrible thing, they have absolutely nothing whatsoever to say about this. So they're lying about health risks of puberty blockers. They make no effort to stop their use for other health needs.