Depends what you mean by a Strava connection? Anything with a USB output will allow you to upload a file to Strava. On that basis the Edge 20 at about £80 is the one. But the Edge 25 can be had for £100, and that has bluetooth allowing you to sync to your phone and get instant wireless uploads to Garmin Connect / Strava – for the sake of £20, that’s where I’d spend my money.
Also just noticed that the 20 and 25 have the GLONASS network. In my experience (rides with lots of steep valleys and some woods) this makes a big difference to the tracking accuracy if your purpose is matching Strava segments. I went from an Edge 500 (no GLONASS) to an Edge 510 (GLONASS) and I certainly wouldn’t contemplate a GPS that didn’t offer GLONASS support now.
Just my two penn’orth, of course 😉