Layers and a light waterproof jacket are always the best advice, that way you are prepared for all weathers. Light cotton trousers and short sleeve tops plus a sweater/cardigan for the cooler evenings during the summer months, then warmer trousers and long sleeves for the autumn/winter months. Good comfortable walking shoes advisable for the day’s activities.
The cost of making calls and texting from the UK on a non UK phone can be costly and we would recommend purchasing a UK SIM card that will offer better value for a low cost. These are widely available on arrival or could be pre-arranged, if you prefer.
A must have that will be much cheaper to buy from home and bring with you. They are available all around the UK, but will probably cost you more.