The promising midfielder feels he owes a debt of gratitude to Posh for helping him mature on and off the field and pushing him closer towards his ultimate goal of making his first-team debut for United.
After appearing on the DHL tour, he is striving to finish the pre-season on a high and keep himself in Sir Alex Ferguson's thoughts ahead of the new Barclays Premier League campaign.
"I'd love to play in this one," he told ManUtd.com. "I got on well with everyone and would love to see them all down there. I was there for eight months and made a lot of good friends that I still talk to now."
It was a culture shock for the teenager to head south and live away from home whilst also trying to deal with integrating into Darren Ferguson's squad.
"I was living on my own down there and had to do my own washing and cleaning, so that was one side of it!" he explained. "I had just come straight from the youth team and wasn't really my own man so I had to make that transition and it helped me mature on and off the pitch as well.
"It just helps all round and in general terms. Being on the pitch, you get experience but I didn't start as many games as I wanted. Yet I was playing men's football which is about three points on a Saturday and not just about development. I learnt a lot and became a man, I think."
The rigours of league football helped Tunnicliffe hone his game as he is renowned for his tough tackling in the midfield.