Ah Scotland! So, the message of providing as much light/sun as possible is definitely one to keep in mind.
Be very sparing with water, especially if the space the plant is in is humid. In a way having the plant 'underpotted', might be an advantage - not much soil around to stay wet long after watering.
You may have guessed from my user name, that I am Dutch and I used to grow Cacti when I still lived there and had some golden barrel cacti that I kept in the same pot for years (my parents have them now and they are still in the same pot), they get by on so little water and still grow. So that is something to keep in mind.
Here it is the start of April and it looks like we are already well on our way to our summer heat, but a lot of things are about to flower. This is a picture of an Echinopsis that is working up to a lot of flowers, so you can get a sense of what developing flowers should look like, I will try and update with a picture when the flowers are open:
My wife and I visited Scotland a couple of years ago. Found a nice AirBnB somewhere just north of Inverness and did a lot of day tripping. It was during the height of our summer and we loved the cooler and wetter weather. Had some great sunny days as well.