I do not know the strength of your argument but the other side appear rattled, many employment claims to an Employment Tribunal are settled before the Tribunal, I suggest you have a realistic sum in mind that you will settle at and accept if this is offered but in the meantime prepare for the ET and make sure the other side know you are proceeding.
The Disability Discrimination Act 1995 states:
“a person discriminates against a disabled person if (a) for a reason which relates to the disabled person’s disability they treat them less favourably than they treat or would treat others to whom that reason does not or would not apply and (b) they are unable to show that the treatment is justified.”
One word of warning make sure the amount that you are prepared to settle for is realistic, if it is too high there is little incentive for the other side to settle and the offer may came very late, the day before the ET is not unusual.