This has been covered before. Basically, it's completely legal as long as the pilot also pays some money towards the cost of the flight, and therefore doesn't make a profit. The pilot can also not fly as a taxi. He/She 'sells' seats on a flight they ALREADY have planned. It's no different to me posting on Facebook to my friends and family: 'Hi all, I'm flying from North Weald to Norwich on Friday 28th at 10AM. I have 2 spare seats available and if you want to come with me, just chip me £30 each'.
If, however, someone approached you and said 'I'd like to go to Norwich on the 28th and I'll pay you the £130 it'll cost', then it's more like an air taxi, but good luck proving that is the case, and not that you decided that's where you wanted to go.
I think it's a great idea. People who love aviation helping out a new pilot build their hours by cost sharing.