Castle recommendations

If you are heading south, how about Leeds Castle, in Kent? We stayed there last June and it was truly amazing. The price for a hotel room in one of their B&Bs (old stables) is very reasonable. I booked directly through their website at https://leeds-castle.com/ You can actually stay in a room in the Castle for a higher price. The views were amazing and you get to wander the grounds after the day visitors have left. The cost of the stay also includes a ticket to the castle and grounds. We stayed for 2 nights and practically had the place to ourselves (mid-June, when UK schools are still in session). There are hourly train services from London Victoria to Bearsted, which is the nearest station to Leeds Castle. The entire journey takes around 1.5 hours. You can taxi from the station to the Castle.

Do you have areas that you are interested in visiting or are you more concerned about staying in the castles and you will build your trip around that? Will you have a car?

Way back in 2013, my husband and I spent two nights at Langley Castle in Hexham. It was not too over the top expensive and we enjoyed having drinks in the drawing room, followed by a great dinner in the restaurant. I see that they are still operational with excellent Google reviews.

Over near the Wales border is Thornbury Castle Hotel. It is pricey and having a rental car to get to nearby sights might be a good idea.

Muncaster Castle in Cumbria- you stay in the Coachman's quarters, not the actual castle, but you get free entry into the gardens at any time (even after hours) also into the Hawk and Owl Centre, and reduced entry into the Castle.

We stayed at Barcaldine Castle near Oban in Scotland.
https://www.barcaldinecastle.co.uk/ it's a bit pricey and remote, but we enjoyed it for a night.