u/Whole-Obligation9400

Hi, planning to stay London Heathrow bath road premierinn. But we have 3 adults, one of us just turned 18. Could we get away check in her as a 15 year old, or will they ask everyones passports? Or is there some other way to sneak the third one in? What i have read that premier inn is busy, but our flight will land 22.00 and would be there late, is it busy at night also? Is it possible to sneak past the receptionist and use self check in? Should i do check in by myself only and other two will come in later? Would book any other hotel, but thats only one with normal price. Anything else i should keep eyes open?