OP -- re the toilet issue, lots of people with cp use a Close o Mat toilet which basically does the washing and drying automatically www.prismmedical.co.uk/products/clos-o-mat-toilets. Note the loo, whilst expensive for a school to install, can be used by non disabled people in the normal way, so is not necessarily a one off 'special' purchase.
On the education issue, don't know if my son's experiences will be useful to you. He has CP, uses K walker, can't dress himself, needs help with eating or drinking, impaired speech, very wobbly. He was the first child with his level of physical disability to go to a local ms primary, where the staff and head were very supportive and prepared to do a lot of learning on the job about how to handle his needs. He had good experiences, although school was probably not as academically challenging as he needed -- good for learning social skills, though.
When it came to secondary, we specifically went for a school with previous experience of including students like DS. We wanted DS to be able to achieve academically and be concentrating on how to do this, rather than having endless discussions with a school which had never had a student like him about how to manage school lunches, transfers between lessons, how the laptop would be used, what the TA would do etc. For example, the school was big but had automatically opening doors and a lift, and had already worked out that DS would need permission to leave lessons a few minutes before the end so he could get to the next class without being killed in the rush. They also had a table in the canteen at lunchtime where students who needed help with food cutting up/feeding could sit with some helpers. (In fact DS soon decided he was having none of this, and got his mates to give a hand, but useful that the systems were already in place in the early days).
I certainly would not recommend witholding information about your daughter's support needs, as this will just mean she's left to sink or swim in a big school from day one. I would be looking for a school which was welcoming but realistic. For this reason, I would be asking some very detailed questions of the grammar school, including what adjustments they will make so she can take the entrance test with the same opportunities to succeed as other applicant, and how they will support her academically as well as meeting her care needs.
Our experience may not be typical, because we do not live in an area with lots of grammar schools (Kent). We are in inner city London where there is one prized grammar which everyone tries to get into. DS is highly competitive by nature, and with straight As and A*s at GCSE was offered a place in this grammar school's 6th form. The school were reluctant to meet us to discuss exactly how they would support him as they thought they could just work it out when he arrived but we did eventually force a meeting where it turned out a) the SENCo was a fairly new and junior member of teaching staff and only did the role p/t and knew very little about students with physical disabilities (their small disabled intake was largely students with dyslexia or autism and most of their support was focused on developing organisational skills); b) rather than having a TA take notes for DS in lessons, they felt this 'would be disruptive to other pupils' as DS would direct the TA as to what to note and his speech is quite loud and distracting, so suggested DS simply take a photocopy of another student's notes (they could not begin to see why we objected to this); c) the grammar also said they would be extremely reluctant/unlikely to apply to exam boards for extra time for DS in exams because he dictates answers because 'giving him extra time would be unfair on the other students'. (DS is very good at using the laptop but because of poor hand function his typing speed is very slow with a lot of errors, so frustrating when he needs to get ideas down, hence the dictation. Extra time in exams for disabled students who can make a clear case for this is fairly common).
DS realised he was basically being set up to fail, so turned down the grammar option and stayed at his previous ms comp, where he achieved top level A levels, and got a place at an Oxbridge college from which he has just graduated with a 2.1. Incidentally, the college and university were far better at meeting his needs -- the grammar was definitely very hung up on being 'selective' rather than inclusive.
HTH