Posting this just in case it helps someone

If anyone in the future reads this thread and is fighting their school on this then follow the link to the UKMT page on this
https://sites.google.com/ukmt.org.uk/challengehandbook/competition-guides/access-arrangements

You are allowed rest breaks or any other access arrangements in the first round of UKMT challenges. I am posting this so if someone looks this up they will find this post. Ignore the following, I'm adding keywords.
Are you allowed rest breaks in senior maths challenge?
Are you allowed rest breaks in intermediate maths challenge?
Are you allowed rest breaks in junior maths challenge?
Are you allowed laptop in senior maths challenge?
Are you allowed laptop in intermediate maths challenge?
Are you allowed laptop in junior maths challenge?
Are you allowed access arrangements in senior maths challenge?
Are you allowed access arrangements in intermediate maths challenge?
Are you allowed access arrangements in junior maths challenge?

https://ukmt.org.uk/senior-challenges/senior-mathematical-challenge
Nothing here to say laptops are allowed ...

https://sites.google.com/ukmt.org.uk/challengehandbook/competition-guides/access-arrangements
They are allowed.

https://sites.google.com/ukmt.org.uk/challengehandbook/competition-guides/access-arrangements
They are allowed.

It doesn't menttion laptops though.

It says they honour all access arrangements, this includes word processors (laptops)

Yes but you need to write on the special answer sheets in pencil! A laptop can't do that!

Doesn’t mean you cant do the working out on a laptop. Most students who type in exams will be able to fill in the boxes on the answer sheet and if they are unable to do so then they should be allocated a scribe for this.

So a laptop is a waste of time isn't?

No, not if the student wants to type their workings out because they have a condition which makes writing slow and/or painful for them! Some students would find having a scribe working with them for an hour or so very overwhelming and independence should be encouraged wherever possible.

How much writing is actually needed for the SMC though - very little.
Scribes work for longer than an hour - my sister scribes at a uni [a degree needed for that level] and some exams are 3 hours!

Depends on the student. Someone with a condition which impacts their writing should not be disadvantaged by this when they could use a laptop.
I am aware of this, i simply said an hour or so to illustrate that even a shorter amount of time could be challenging.

No - it should be their normal way of working ie all day every day or the school is acting fradulently.

I agree, i think you misunderstood my comment.
If a student has difficulty writing and their normal way of working is use of a laptop then they should be allowed this in UKMT papers. They could of course have a different adjustment for maths, such as a scribe or extra time for writing if this is more appropriate for them. This again would also be their normal way of working.
What i was saying is that if a student had significant difficulty with writing was disallowed from using a laptop in a paper they would either be disadvantaged or require a scribe perhaps to write for them. For some students, using a scribe for a paper would be very difficult.

You are allowed rest breaks or any other access arrangements in the first round of UKMT challenges. I am posting this so if someone looks this up they will find this post. Ignore the following, I'm adding keywords.
Are you allowed rest breaks in senior maths challenge?
Are you allowed rest breaks in intermediate maths challenge?
Are you allowed rest breaks in junior maths challenge?
Are you allowed laptop in senior maths challenge?
Are you allowed laptop in intermediate maths challenge?
Are you allowed laptop in junior maths challenge?
Are you allowed access arrangements in senior maths challenge?
Are you allowed access arrangements in intermediate maths challenge?
Are you allowed access arrangements in junior maths challenge?

If you have to use a scribe then it isn't difficult! Some people, and I've taught one, cannot write because of cerebral palsy.