Hi! I'm sorry you've not got many responses but I can answer a few questions for you. It's worth going onto the LitterTray rather than Pets as that will be full of cat owners, fosterers and vets.
We live high up in a flat... no cat flaps.. balcony too high to allow cat on I think (do have net but that's to keep things out not in) so is there really such thing as a house cat? would I have to walk it?
Some cats, especially those with conditions like FIV, are encouraged to be inside when adopting them from rescues. Don't worry, these conditions aren't transferrable - it's just a cat specific condition. Some are strays who really don't suit the outdoors or they are elderly. My cat is a bit spooked of outside so she doesn't go out much. However, most healthy cats will want to at least explore. Again, if you buy from a breeder, the breeders often specify that they should only be an inside cat. You won't have to walk them though
I've a diagnosis of OCD, pretty much recovering but unsure if would be good or bad for my MH - I realise I would have to touch cat food, cat litter, cat etc. Seems manageable now but in not so distant past I couldn't even have contact with children without needing to decontaminate myself swiftly.
I am not very sure of how your OCD is but pet stores do have disinfectants, gloves and you can get them latex bibs to help if you needed to. Plus, if you got clumping cat litter, it'd mean you'd only have to scoop out the wee or poo clumps with the scoop and bin, flush or put them in the compost if they are those kinds of litter. It's a great sense of responsibility once your child grows older if he is up for it.
I definitely couldn't cope with kittens... is spaying unethical? I have no idea
Spaying is really recommended and I have spayed my cat and it's not unethical at all. One cat can produce 20,000 in 5 years and there are already enough in rescues anyway. It will stop behaviours like marking, fighting, wandering too far out and certain cancers and diseases. The op won't change their personality though.
Do they cost a lot? Food, vets, vaccines?
They can be expensive if you don't have insurance. Best to shop for insurance. Vets are private businesses so it's best to shop for their prices as they are all very different but kittens usually require 2 vaccinations and a booster once a year. Vets can give prescriptions for flea treatments, dewormers and other necessary meds beyond the basics so you can order them online cheaper. Food can be bought in bulk from zooplus.co.uk so that's a good thing. I give my kitten dry so she can snack on it whilst I'm not home or at night when I'm asleep and she wants food. That keeps them a bit full so you don't have to give them wet food all the time which can be expensive.
Are they like dogs in that some breeds would be better than others with children?
Some might say so. I haven't got a pedigree, I have a domestic short hair which is no specific breed and for them, it matters in the way they are exposed to things in the first 8-12 weeks. If you get a good one that is used to children of all ages, that's great. 6 is a good age where they can be responsible and not chase their cats imo. Boys are apparently more affectionate and girls can be aloof which I have seen but it's not always true.
Will a cat be lonely by itself if we are out? When you go on holiday do you have to spend a fortune on cattery?
It is advised that a kitten under the age of 2-4 months isn't left for too long if the house isn't kitten proofed but I left my one at 4 months for a whole working day. She probably slept the entire time. Catterys can be about £15-30 a day or night (depends on the cattery) and they'll be looked after and be not very lonely at all. I am considering sending mine when I am going away on holiday. Another thing is where you can arrange for a petsitter to come 1-4x a day to clean after them and play with them. You can ask your vets if they know of any or search online - there will be some companies who offer this.