In planning out my UK visit, I find myself with an extra day between leaving SE England and arriving in Manchester around 48 hours later. So trying to not blindly choose a city/town/village based on my complete ignorance of the area, but rather open up to suggestion from BC.
Thanks in advance! 
Sean
Peak District National Park? Chatsworth House is worth a visit, lots of little villages to see, try a genuine Bakewell Tart in Bakewell. Bakewell is about 1 hour from the airport by car.
Peak District, as above. With some interesting early industrialisation.
Or diverting the other way: Shropshire, including Ironbridge, and a little bit of Wales, as often extolled in this forum.
Jonathan
When you say SE England, where more specifically do you mean? Depending on your starting point, Oxford may be en route for you. The city, the University, plenty to see and over 800 years of history to soak up. https://oxfordcity.co.uk/
For driving or sightseeing?
If the latter urban or rural?
History or nature?
Stephen
Democratic dissent is not disloyalty, it is a positive civic duty
A road less travelled might be an East Anglian amble up to Duxford ( wonderful air museum ) , then East via Thetford Forest to Hethel (I'm sure Classic Team Lotus would give you a look around if you tell them how far you've come ) , then North to Lincolnshire over the fens and then that lovely drive across the Wolds to look at Cadwell Park (usually something going on), back West to my favourite cathedral in Lincoln and then over the Pennines to Manchester, where it will almost certainly be raining ...
Warwick castle is a great visit if you like that sort of thing. One of the few complete castles in the uk, within a very traditional town.
Terry7
This will be near the end of a 2+ weeks long driving holiday that already has me visiting Edinburgh, Wales, Ramsgate, and many points in between - Newcastle, Carlisle, Leeds, Nottingham, Cardiff, Lewes, etc. A local British ex-pat recommended Oxford to me with no hesitation, so that was my first thought. Already planning to visit Nottingham, Birmingham, and Bedford earlier on.
I appreciate the suggestions. Now I've got some research to do on those. Thanks!
For heavens sake don't miss Bath if there is any way to do it on your trip. No other city like it for it's style of architecture view of the hills from the city etc.
Personally for me it edges York as the most beautiful city in England but that's just personal choice. If you do decide to do it PM me and i'll try and give you a tour.
There might be some ideas here: https://www.theguardian.com/travel/2023/mar/15/where-tourists-seldom-tread-part-4-five-uk-towns-with-hidden-histories
Home of LADS, Bury, is first one to visit
Another vote for the Peak District.. a quick Google search will help you visualise the area. As a local I know I'm biased, but it's a beautiful area.
Ping me when you're in the area and I'm sure we can extend a local Seveners welcome to you.
Cheers
Rog