Three months in Europe in 2021

If the Lakes interest you, I'd propose also spending some time in the Derbyshire Dales and Yorkshire Dales. You may find the Fens in East Anglia unique.

Moss, you don't say much about what sort of things interest you - or not interest you - so we don't have much to hang our hats on.

Nigel,
Thank you for your post. Yes, I failed to include my interests and perhaps some personal information that would have been helpful. Thank you for pointing that out. I'm 66 year old male, traveling alone r and in good health. I will be working remotely 15 hours a weeks via computer/online, so a somewhat slower pace is required for me. I am very interested in historical buildings and all things history, smaller towns, and the outdoors. I'd much rather meet locals than be impersonal and anonymous. I enjoy all kinds of food. I will not be driving any of the trip, but relying on train and bus.
Thank you

I had a great time tracking down the Charles Rennie Mackintosh buildings in Glasgow and Helensburgh.

Did you mean come back along the west coast? Seems redundant to go up and back along the east side of the country. I don't know that much about that but have spent time in the west. Would happily spend more time in

Cornwall - amazing scenery, Tintagel, St Michaels, etc
Bath - the Roman Baths, the Abbey, wonderful architecture/walkable city with Stonehenge nearby
Wales - again lovely scenery and lots of castles
Lake District - is lovely as well.

We only saw Edinburgh and are planning more time in Scotland to include Glasgow, the highlands and maybe the islands. Edinburgh and Stirling castles - well preserved built on hillsides with awesome views.

Due north of the Lake District is now the city of Carlisle, but 1,800 years ago the area was part of the Roman frontier, defended by Hadrian’s Wall. Three years ago, we started west of Carlisle and walked the width of England, following the Hadrian’s Wall route. You could visit Carlisle and trace some (or all?) of the route. There’s an interesting museum, and a massive castle from later historic times.

Heading from Scotland back down the eastern coast, be sure to visit Newcastle, which was near the eastern end of the Wall. Tours and shuttle buses can take you a bit west, to some of the better parts of the Wall that still stand, and to remnants of Roman forts. There’s also a museum at Wallsend, a town east of Newcastle.

Continuing south of Newcastle by train, spend a few days in York, a walled town with history, architecture you might like, and atmosphere.

We have visited 3/4 of the countries in Europe and all of Western Europe.
Great Britain has amazing countryside. Yes, London is wonderful, but suggest getting out in the countryside.

In 2017 we did a great four week drive tour of England and S. Wales. It included the Lake District which is very scenic. The Lake District is great for outdoors people and things like hiking.

Our trip visited South Wales, which is great. Wales is loaded with castles.

We visited:
Bath
South Wales ( Tintern Abbey, several castles, Cardiff, Tenby, St. Davids and more).
The Cotswolds (don't miss Cirencester, Oxford, Blenheim Palace, Stratford Upon Avon) we used Chipping Campden as our base.
Warwick and it castle on our way to York.
York is a must see. The Minster (Cathedral) is special and has a wonderful tour. Walk the walls, visit the ancient city with narrow streets and great museums (don't miss the National Railway Museum).
Whitby is recommended. Getting there from York you drive over the Yorkshire Moors.
Durham and its quaint city with another amazing cathedral. The Venerable Bede is buried there.
Hadrian's Wall, we stayed a night at Haltwhistle.
The Lake District
Back down south to Winchester, the ancient capital of Saxon Britain.

Other places to visit are Salisbury, Windsor Castle, Canterbury and Stonehenge.

We have plans to visit Cornwall whenever the virus is no longer a problem.

As for the mainland of Europe, there is much to see. For Belgium, Brugges and Ghent in the west and in the east some WWII battlefields as well as Luxembourg.

You mention Hamburg, It was OK, but there is so much more to see in the Rhineland, Black Forest, Bavaria and around Berlin.
On your way to Krakow, consider stopping at the Auschwitz concentration camp. It is important to never forget what happened there.

Prague is great and Budapest is special.

Thank you all for such great suggestions!

I will second Nigel's recommendation of the Yorkshire Dales. However, as you are working, be sure to ascertain the strength of the wifi, assuming you need it, for the location you pick. I know the wifi can go out for days in the winter, but summer is likely a better scenario due to nicer weather. My experience is Grassington, which is a lovely, lovely village, and has lovely walks thru the Dales to other villages, hamlets etc. where one can have lunch and/or a beer.

I suggest looking at Whitby and Robin's Bay for a quick visit as well. York is lovely, but I would rather base in a village like Grassington or in its market town, Skipton. YMMV.

Salisbury has an interesting small museum, in addition to the cathedral. I really enjoyed Cardiff-castles and St. Fagan's outdoor museum. In the area that you're planning to travel, definitely York-I really enjoyed the York Castle Musuem, and we also enjoyed Durham. Wells is on my bucket list.