Madame Trédan's flat at the rear of her house was a comfortable place to stay for a few nights. Upstairs (15 steps), it has a small but adequate kitchen/bedroom and bathroom, with another single bed available downstairs; WiFi is available, though a little patchy. Everything was clean and tidy. We didn't meet English speaking M.Trédan, but managed in French. Access to Rue de la Tréherais is a bit tricky, and some of it is one-way. Limited parking is available - you may need to park very close to a wall.
Parking in St Malô is difficult, but if you use a narrow path and cut through an estate (all the locals do), the flat is only five - ten minutes away from a very good bus service (buy an all-day ticket), which enables you leave your car at home, and a Netto supermarket and boulangerie/patisserie (beware Sunday closure!). With one bus change, you can get right to the old city with its very interesting castle, and maze of streets and shops.
Nearby Dinard is worth a... Plus