SniffwhiffI've never smelled London Fog by Brandt, but I will second the suggestion above and say Moon Magic by Sorce.
I think it leans more lavender than vanilla, and don't find it to be overly sweet. You mentioned you wanted a creamy lavender: personally, I don't find it very creamy. It was quite powdery on me but maybe it will react differently on your skin.
Also adding a slight correction to the above post: there's no marshmallow, cookie butter, or Tahitian vanilla in Moon Magic (those last three notes are in the aforementioned Snow Moon Magic, which I haven't tried).
And lastly, I'll add that Sorce offers 1 mL oil samples and 2 mL spray samples on their website. They often have long wait times, though. Ajevie.com also sells some samples, although I've never ordered from them so can't say if the wait time is less.
EDIT: I see that you're in the UK. I don't know if Sorce ships internationally (they're US based), but Ajevie ships to the UK. And sorry if this was way too much info; I am an excessively thorough person. 😅