The field is currently full of long grass which has gone flat and is a nightmare to get through. I was thinking of hiring a rotovator to turn over what I need
Long grass will wrap around the rotavator tines and you'll have to stop and clear it.
So best to get the grass mown as short as possible before rotavating.
If you are going to rotavate the field make sure you get a powerful rotvator. If a walk-behind type it needs to be the sort that powers both the wheels and the tines - not the ones that you take the wheels off and the motor only powers the tines - that will be very hard work to break new ground.
As I said above my preference (for a decent sized area) would be a mini tractor with PTO driven rotavator - but even that may struggle with virgin ground, and it won't work with wet ground (hence perhaps get it ploughed first).
With a beefie rotavator I suggest you do as large an area as you reasonably can - e.g. if you are hiring it for a weekend. Leaving the soil opened, but fallow, will cheer it up and make it more usable over time. You can put weed killer on any grass / weeds that appear (if you are happy to use weedkiller) and if you want more area it won't take a lot of trouble to get it going where it has already been rotavated - whereas hard packed land in the middle of Summer is definitely hard to convert to a flower bed!
Christine's point about Raspberries is a good one. Some things take a year or two before they come to anything. Raspberries probably won't give you anything in the first year (Autumn fruiting ones might give you a bit). Ditto Rhubarb. Asparagus won't give you anything for 3 years, maybe more. Fruit trees will take a while.So you might want to plan to get those type of crops in sooner, and maybe raising some from seed (Asparagus for example) in "Nursery" beds to save money rather than buying "mature-ish" plants.
Not sure about herb: My Chef tells me that the herbs have to be right by the back door - let alone 2 miles down the road!!