I think my suspicions that it was probably Odin were maybe right.

Last night I tried again with similar results; thought of the runes Os and Ehwaz, pressure point on my forehead, etc.
But last night the pressure moved to my right eye and it felt like someone pressing the heel of their hand softly into my eye socket. I tried to opened my eyes, but my right one remained closed.

I'm not scared of Odin, but I'm wary of him being around when I can't feel Loki nearby (plus the fact I've been pretty cheeky to Odin in past dreams, so I can't help but feel he might have it out for me - disrespect of the All Father and all that jazz).
So I stated my Terms and Conditions, like the first time someone took over.
I honestly didn't believe at all  he'd even listen or take in any of it, but when I finished and said "Okay, on you go", my arm give a massive jolt... so I took that as a 'alright then' and stood back.

He didn't stay for long and his presence didn't feel very strong either - not like the first time I tried it. Maybe I've been trying too quickly and should wait a bit longer before going at it again.