What to wear/pack in England and Scotland in mid July?

You'll either be fine in a tshirt or need 2 layers and a jacket. So cater for everything in between.

Welcome to a UK summer !!

Thank you. Believe it or not, that does help.

Well I thought it was helpful , because I understand that no one can predict the weather , the weather is changeable , and that you are unlikely to need a bikini in either places , but may be fine in a tshirts or sundress , but you could hit a wet cool patch and want to have a sweater or fleece and windbreak/ rain jacket .

For night wear I tend to wear similar to day wear , I may add a nice scarf or wear a nicer top. As I said I tend to wear dresses or skirts all the time ( there are super casual ones not all fancy) and usually bring one pair of jeans or capris depending on wear I am going . For Scotland and England I always throw in a pair of jeans , nicer ones , not gardening jeans , they can be dressed up with a blouse instead of a tshirts and decent leather shoes .

The two most useful things you can pack are (a) really comfortable, well broken-in shoes for lots of city walking and (b) a lightweight rain jacket that you can fold up and carry in your bag.

Temperatures, rain or otherwise - unpredictable.

July can be quite a wet and not-warm month, August is often drier and warmer.

Or it can be broiling and the newspapers will show the photos of the girls at the beach eating ice creams and wearing much of it.

We used to go to the UK regularly in mid-to-late July. Here's what I'd take for a 9-14 day trip (including what I'd wear on the plane):
3-5 short sleeved T shirt or polo shirt type tops
3-4 pair cotton blend pants (maybe one of them jeans)- black or khaki
1 or 2 3/4 or long sleeve button-up cotton blend 'big' shirts (to wear over the Ts as a kind of light weight blazer or jacket) this was to dress up for dinner or for cooler days
1 or 2 scarves- to dress things up
1 pair good walking shoes- black
3-5 bras
5-9 panties
6-12 pair socks
pajamas - could use shorts or yoga pants and T or just long T
1 waterproof windbreaker with hood

I am warm natured and would rather be a little cool than too hot. If you are cool natured, take a cardigan or fleece to layer instead of the 'big' shirts, and perhaps sub in 1 long sleeve T.

I was in Scotland last July and one day, it only reached 7 degrees daytime temperature and there was a cold wind. Ensure you have a waterproof and windproof jacket and waterproof shoes.

Cambridge is more likely to be warmer and drier.

This morning, I left Manchester where it was 15 degrees and misty at 11am and drove to London, where it was sunny and 27 degrees early evening. Pack layers and ensure you have clothes for warm and sunny and cold and wet.

Have been to the UK multiple times in mid-to-late July. Here's what I usually took (including what I wore on the plane):
3-5 T shirt type tops- all short sleeved or possibly 1 with 3/4 sleeves
1 or 2 'big shirt' type button up shirts that can be worn alone or as a some what dressy 'jacket' or for added warmth with a T
3-4 pair cotton blend pants in black and/or khaki
1 or 2 scarves to dress up outfits
1 windbreaker with hood (waterproof- no lining)
3-5 bras
7-10 undies
6-12 pair socks
black (comfortable) walking shoes
something to sleep in (shorts and t, yoga pants and top, long t, etc.)
I'm warm natured and would rather be a bit cool than too hot. The windbreaker stayed in my day bag at all times as showers can pop up at any time. The 'big shirt' was used as an extra layer on cooler or cold days- not many in over 20 trips at that time of year.

If you are cool natured, sub a fleece or cardigan for the big shirt(s), or take one or more heavier and/or long sleeve tops. I also usually took a small travel umbrella, but used my hood more.

Thank you all so very much for your responses. This has been very helpful

It's called Glasgow.