"To be honest, Tatenhill has served its purpose as a cheaper way of getting my PPL, Night and IMC Ratings, but now I want more of a challenge like operating out of a controlled airport, as this is where I want to be with my career!"
At a big airport you are told what to do, at a small airfield you use your own judgment. Not sure one is more challenging than another. You do not have to be based at a big airport to become familiar with with the operation, just fly in. If you get a share and tour the big airfields in France over a summer you will gain the experience with very low landing fees - sometimes nothing at all. I suspect that after your 3rd or 4th visit to one you will wonder why you thought it was a challenge.
Rod1