It's a fairly standard green manure mix. Vetch and peas add nitrogen, they all organic matter when dug in.

Overwintering green manure is very useful as it prevents soil erosion, capping and compaction. And all the nutrients are kept in the plants instead of being washed away, which then become available as the plant matter breaks down.

For quick results you can't beat mustard as it grows so quickly and discourages a few pests, although you can't plant brassicas straight afterwards.

So, I would say that green manure is a good idea and it is quite an easy way to improve your soil.

Hya Thanks very much for your Advice, i set some Seeds away and they came through very quickly indeed, i just hope i can still put my Onion Sets in the same place, as you know some things dont l;ike fresh Manure, but i shall ckeck on it first, Thanks again