<<I'm currently training for my ppl >>
I think that may be the problem. You are not a pilot - yet - so in the eyes of those you spoke with you may be viewed simply as a member of the public. Don't take that the wrong way, but you can imagine if they let in everybody who said they had an interest..... As suggested, you'd stand more chance trying at the weekends but I think a better bet would be to try and arrange an official visit for pilots at your flying school...
I'm long retired but these comments are based on my experience at Heathrow at West Drayton.
Good luck with your career.