Whilst I have little direct experience with the Benelli family of shotguns, I can attest to their reliability, even some of the older guns. I know quite a few shooters who have had the same guns for over 25 years now.
Personally, my budget semi-auto shotguns of choice come from across the pond, with the SX3 and Mossberg 930, both bought used and can be found either under or a hair over your £400 budget. They dont run light clay loads unfortunately, but no issues with any other loads game or clay I have put through, and patterning on the SX3 with steel wildfowl loads has been really good for me as well.