We're a 64 year old couple planning a UK trip, our initial rough concepts for our itinerary are presently:
Fly into London (4 nights) then fly to Inverness/Orkneys
Orkneys (hire car for site seeing) 3 nights then fly to Edinbough
Edinbough (3 nights) then hire car to tour central Scotland
Central Scotland (4 nights) ending in Glasgow, then to
Lakes District (3 nights) then to
(Not sure yet) (2 nights) then to
Costwolds & Oxford (4 nights) then to
Salisbury & South West (5 nights) then return car on way to back to London
London (2 nights) then home
Would appreciate your help with the detail

I don't have a lot to add right now, but will go over your itinerary. One thing I'd add when in the southwest is to visit the City of Bath.

Hi
A couple of suggestions for your two nights after the Lake District
1) Trough/Forest of Bowland in Lancashire (not actually forested!). Very easy to reach from the Lakes, absolutely beautiful area pretty much overlooked by tourists - a bit of a well kept secret really.
www.forestofbowland.com
If you have a look at the website above, follow the link to 'Discovering' and then 'Towns and Villages' you can click onto a map of the area and read a bit more about the villages themselves.
It also has some fantastic pubs and restaurants that have a very strong emphasis on the local food (which is superb). A few favourites of ours (we visit this area several times a year) -
www.innatwhitewell.com (this does rooms too and is set in the most pastoral setting you could imagine (cows, streams, meadows)
www.thethreefishes.com
www.theredpumpinn.co.uk
2) The Yorkshire Dales
The Dales cover a very large area but you could easily visit the western side of them for a couple of days. Again a beautiful area.
www.yorkshiredales.org.uk
There's a lot of info on here already about visiting the Dales so I won't repeat it.
Both areas above have lots of farms that do a very well priced bed and breakfast if that appeals to you.

Perhaps you could give us some details of your interests - hiking, museums, shopping, etc.

What time of the year are you considering for this trip?

I like the Scottish bit of that. I can help with Orkney, Edinburgh, Central Scotland (a bit) and Glasgow (a bit).

What would you like to know?

Morgana

please don't tell many people about the forest of Bowland - it's a secret we like to keep to ourselves.

Oh and forest in the title is the old meaning of a hunting ground - so only a few trees.

Penstone

Either Yorkshire or Lancashire would fit with your trip. York could use a couple of days, Chester is interesting.

But as already stated tell us what you are interested in.