@donnellysdogs
This really depends on how far you want to take it, personally I'd be annoyed enough to go back.
Meet the manager
ask for the reason why you are being excluded, as you have a medical assessment that states you are able to participate, and should not be excluded for medical reasons.
If they continue to exclude you simply based on a blanket ban for T1, tell them they are in breach of the 'Equality Act 2010' as you have a recognised long term disability, which is a protected characteristic as per Part 2, chapter 1, section 6 of the Act.
The disability is defined in Schedule 1
5(1)An impairment is to be treated as having a substantial adverse effect on the ability of the person concerned to carry out normal day-to-day activities if—
(a)measures are being taken to treat or correct it, and
(b)but for that, it would be likely to have that effect.
They are in direct contravention of Part 3, section 29.
(1) A person (a “service-provider”) concerned with the provision of a service to the public or a section of the public (for payment or not) must not discriminate against a person requiring the service by not providing the person with the service.
They may try to claim they are providing the service, but it is not the service, it is an unsuitable (for you) lesser alternative service and this is in contravention to
(2)A service-provider (A) must not, in providing the service, discriminate against a person (B)—
(a)as to the terms on which A provides the service to B;
(b)by terminating the provision of the service to B;
(c)by subjecting B to any other detriment.
They should, hopefully, fairly quickly agree with you.