Hello -
We will be in Ireland and Scotland over the same time period as you. I am packing basically what I packed on our trip to England two years ago at the same time. I do sort of what is called the "capsule" packing method. I stick with one color theme and then pack layers. I also use the compression packing cubes. We also will be traveling with carryon sized luggage albeit will likely check them. OK, what I packed last time and it was perfect and all fit into my carryon sized bag as well as a backpack. My base color was black and grey with teal blue as my accent color on that trip.
My packing list - all fit into my Eagle Creek Tarmac 22" bag as well as my Pacsafe backpack.
(2) pairs pants - blue denim jeans - today maybe the skinny jeans that can also be rolled to an ankle length. Grey Prana pants that fit like jeans but don't look like jeans and can be dressed up a bit. You could opt for more of a nylon type hiking pant in black that can be dressed up.
(1) Skirt - I brought a black Patagonia travel skirt - ExOfficio has a nice one as well - check REI.
(1) shorts - if you get hot and prefer to wear shorts in warmer weather they do not take up much space. I brought a pair of Kuhl cropped pants that roll up just above the knee.
(5) light weight short sleeved travel t's - base layer and worn alone if warm - a mix of black, grey and the accent color. I avoid cotton and go for the Smartwool 150 weight light wool which is comfortable in all weather, or Ibex albeit they are now out of business. Prana, Patagonia also carry good choices. REI brand as well.
(1) long sleeve travel T - same description as above.
(1) Polar fleece type - I broght a Kuhl teal pullover on the last trip
(1)shawl style very lightweight travel cardigan in grey - can dress up the jeans or wear with the skirt over a T
(1)Nylon 3/4 sleeve button up shirt - can wear over a T with the skirt, or with pants, or shorts - extra layer.
(1) vest - polar fleece, or my favorite - Patagonia Nanopuff. I had grey on last trip, Oxblood on this upcoming trip
(1) good rain jacket - I prefer the longer style - REI has a great trench style that is just to upper thigh.
(1) light hiking shoes - can use running shoes as well which can duel purpose for running or working our if you're so inclined.
(1) pair of comfortable walkable dressier shoes - I prefer a mary jane type that can be worn with the jeans, slacks or skirt - There are many choices. Last trip I wore the Merrill Maryjanes and walked miles in them.
(1)scarf to dress up, add warmth, color - find one that ties it all together.
(7) pairs of underwear
(2) bras
(1) running bra
(1) very light cropped running tights
(1)running tank but also wore one of my base layers
(1) very lightweight pullover for running.
(1)LLBean medium toiletry bag with very small amounts of my essentials
(1)small makeup bag - Sophora is a good source for travel size cosemetics
(1)decent size carryon backpack - last trip I used a Pacsafe and kept all of my make up, vitamins, rain jacket, polar fleece, camera with me in that.
(1)PacSafe purse.
If all your stuff coordinates in color you can eliminate as needed and just wash more. Everything should pretty much go with everything so you can grab and go and layer as necessary.
Have a great trip!!!
Rhonda