Seem to be having a catch up this afternoon with gaps. Three left on this London Underground Quiz. Again no number of letters.
No.20 Duke of Cambridge's bolthole and meeting place
No.24 Ant & Dec's alma mater
No.47 Dick Whittington's home?
Thank you
Thank you sandyRoe and JJ109 very cleverly worked out. Thank you Mamyalynne missed the message from the setter. Grange Hill is a good answer. Much appreciated.