I tink the reason we got respite (just summer) is that we have no family in the country and I was ready to leave (call me evil, I know)
I think from their vpov it's cheaper to use respite for summer than deal with a single parent who cannot cope.
WRT to not offering anything to nt kids I am totally against that; i've seen enough kids raised by parents who simply will not deliver anything close to care, and there's also kids being cared for by other relatives, disabled or sick parents, young carers themselves..... kids in need only but that's not only sn, by a very, very long stretch (too long in field picking up piece4s sadly).
It shouldn't come out of sn budget though (don't think we have aiming higher here).
Around our way the council pays for sn placements but lays on plenty of playschemes which are paid for, but affordably so. We've used those in the past- eg tennis day for ds2 for a tenner. The university also runs half term and summer playschemes open to anyone which are cheaper than many palces- £16 per day iirc (few eyars since I used it though). theyc an, actually, manage some sn and are always willing to give it a go, and their facilltiies are accessible (complete with hoist and stairmaster).
That isn;t SSD provision though obviously.
TBH I son't see why better off people with SN kids should get things for absolutely free- i'd be happy to pay a contribution. Actually I hink they should suggest a voluntary one, we'd try to find something, and I mean genuinely anonymously voluntary: most yers we'd pay a fortune from DLA just trying to keep them occupied, no reason why SSD should't see a few £'s from that. But of course how expenses are used vary- note veryone can.