When I used to dabble in 'N' I experimented with both code 80 & 55 track, the rail joiners are the standard N gauge ones suitable for both code 55 & 80, the only thing you would need to do was to shim up the code 55 to make a smooth transition to the code 80, so as far as I can understand it, the Peco code 55 should be able to join up with the code 80 from Hornby.