Ref switching to IFR, all "Nos"! Firstly you wouldn't go from VFR to IFR in snow due to icing, assuming helo is is not icing approved, which only some bigger types are. Nor would you switch at low level, unless you were intending to climb up to MSA in which case you'd need to know that icing wasn't a risk. Which it almost certainly would be. And finally you would go IFR at low speed - well not very low speed anyway - as there is always a minimum IMC speed - typically 55 kts.
Flying in snow can be ok though depending on acft (and snow) type, and severity. Not sure what Kent run but if AS355, off top of my head recall limit as unlimited time over 1500m vis, 10 mins from 800m to 1500m and no go under 800m. Of course not ideal and you'd still keep a careful watch on ice/snow build up. Where the engine air intake is positioned is important - eg 206's without snow baffles are bad news as snow can block up the forward facing intake quickly.
Prob not a drama. Don't forget snow looks a lot more when travelling at speed. Especially at night!