I like staying in aparthotels and have stayed in many throughout the world. In fact, I'm in one now.
I can't help with Montpelier.
They are run just like hotels but you have a kitchen in your room. There is usually a laundry room with washers and dryers (sometimes free, sometimes not), sometimes there's a washer and dryer in your room, breakfast is included in some, usually a fitness room. Housekeeping is included but not always daily. Mostly a 24 hour reception desk.
Some fo the more notable chains in Europe are:
Staybridge Suites,
Residence Inn,
Fraser Suites
Citadines
Adina Hotels
Adagio Hotels
Staycity (incuding Wilde by Staycity)
Locke Living
Hyatt House
Some apartment buildings have been converted to aparthotels but are not part of a chain. What they offer may be different. Do your homework and look at reviews at both Tripadvisor and Booking.com.