Hi Dan
I had a similar post to yours, about a year ago, before I started the PPL. My idea was to do the same, but ask for money. Being extremely uneducated on the subject of course! I was going to post adverts round my university to see if anyone was interested in 'local flights' - or pleasure flights if you like. The thing is, as you know, you can take no profit at all, and must pay no less than the equal share of the flight. That is the money side of things, and unless things have changed, I would be careful. With regards to the advertising though, I think this is a different matter. I am not too sure on this one, so hopefully someone else can shed a light. I do know though, that the CAA come down heavily on people who break the rules, especially in this department.
Best of luck
Maz