Speakers: If you're in a conservatory then that probably means there's quite a bit of glass around. Hard surfaces reflect a lot of sound, and so that sound bouncing around makes it harder to hear what the speakers are doing directly because the direct sound is fighting against the reflected sound. If you want to hear the difference that the room makes to sound then try listening to and comparing the echo from a clap in the conservatory to a clap in the bedroom or somewhere else with a lot of soft furnishings. There'll be a lot less of the tsk-tsk-tsk sound bouncing around in a room with soft fabrics absorbing the reflections. Carpet and window blinds in the conservatory will help a lot.
Electronics: A Sonos Connect running in to an AV amp or 2 channel Hi-Fi amp makes a lot of sense if you plan to add Sonos to other rooms in the house. A Sonos Connect Amp will quite happily run a pair of Hi-Fi speakers but it will struggle to be an effective hub device to handle multiple AV sources. The TV could act as a switch for the sources and also as a way to convert audio via HDMI in to Optical. You'd then need an Optical to analogue audio converter box to get the sound in to a format that the Connect Amp could use. That's all doable, but it just seems a bit messy for what's supposed to be a main TV/music system.
As a standalone solution for accessing stored media files and streamed music there are alternatives that will work nearly as well such as the built-in media streamers in network AV amps. So, as good as Sonos is (and it is very good indeed) going Sonos depends on your plans for the rest of the house.