can anyone recommend a rotavator to dig up lawned areas to make new large beds? or is this plan a disaster in the making
A rotovator won't dig it up, it will just cut the grass and mix it through the soil. Far better to take your spade and lift the grass with as little soil as possible. Stack it somewhere out of the way and dig over your new beds.
A turf stripper would remove the top layer if it's too big an area to do by hand as hogweed illustrates.
If you are converting lawn to flower beds you are better off removing the existing grass as hogweed and Fairygirl have suggested. There is a probability that the grass will regrow in the flower beds if it's just dug in using a rotovator. If you do decide to rotovate I would hire one as you are going to need one with quite a bit of power.
My neighbour has a rotavator of considerable strength and we recently used it to do just as you're suggesting julian19.
The soil is lovely and light and I saved a lot of turf lifting but I am having to weed out the re-growing grass.
I've done two other areas by lifting turf and digging over and it is much better in the longer term. If you don't mind weeding or you're prepared to dig it over again for a year or so before planting permanently then go for it.