Last min cottage in the UK - any (not Airbnb) suggestions of where to look?

[Yellowingtrees]

I am losing the will to live - for various reasons we've left it crazily late to book a few days away at Easter and I can't find anywhere that looks right (and isn't insanely priced).
Our limitations:
3 beds - we have 2 autistic teens who need own bedrooms so house can't be too cosy/bijou
Small dog
No more than 4 hours from London
Ideally walks from the door
Available for 5-7 days between 1st and 9th April

Any brilliant suggestions?

Does it have to be a cottage?

Pick an area and ring (yes, actually talk to a person) the local tourist information office.

Stags cottage North Molton 3 bedrooms holiday home. Walks over Exmoor and close to coast/beach. Under 4 hours from London £564 4 nights between your dates

We have stayed in some lovely places via https://www.farmstay.co.uk/

I will always add https://www.sweetcombecottages.co.uk to these posts. Reasonably priced cottages in East Devon. I’ve used them loads for last minute escapes!

We often use Sykes’s cottages. Reasonably priced and lots of choice

Norfolk hideaways website

Walcot Hall in Shropshire is wonderful

Have you looked at Independent Cottages?
We booked a lovely cottage through them. There are no agency fees to pay so we found it cheaper than using Sykes or similar agents.
The other advantage is you are able to deal with the owner directly.
My son is allergic to feathers and I was able to arrange with the owner that any feather filled cushions etc would be removed before our arrival.
I hope you find somewhere.

Thank you all! Brilliant different suggestions!