I've been told you cannot park on grass verges unless you own the bit of land the verge is on. I looked at the highway code and could find nothing about it except don't use them as cross overs.
Basically there is a large piece of grass in front of our house, to drive onto it you drive up a kerb onto it, but not across a pavement. There has been vandalism down our road and this is the only place left to park so you can keep an eye on your car. If it's not allowed do they give you a warning or do they just give you a fine on the first time they find it - it's a residential cul-de-sac so not causing anyone any problems.