>>/61209/
the usual wisdom is that the only real consequences are from (1) actually doing something with them or (2) failing to disclose details when asked in writing by admin. 
at least in the US all [serious] institutions outright ban any mixing between undergrads/grad students/lecturers regardless of program, etc.
no idea how it works over there but if your earnestly worried about it just do  >>/61264/, this can really only bite you if your stupid enough to do something that can plausibly be construed as romantic favouritism and it comes to the attention of admin. dont be a retard!