Scared to Offend Him

If you feel that he would be offended, then I am that you have correctly anticipated his reaction. The best way to handle this is head-on.  Say, "I want to back to Scotland for 10 days on my own, but I am scared that this will offend and worry you. Am I right?" 

If he confirms your fears, then talk about what offends and worries him about your going alone.  Perhaps he fears that you don't love him as much any longer or that you are pulling away. Let him tell you, then you can reassure him that it is normal for even the most loving partners to need time apart.  

If he is still stuck, then you might encourage him to dig a bit deeper within himself to see if he can figure out what wounds of childhood may be being opened. Making that link should help him to give you the room you need without his freaking out.   Let me know what happens.