What a lovely place to be. I am so jealous of that beautiful walled garden, but it's a life's project on its own to tame and bring back to life. Are you on your own there or do you have family to help? Yes, you definitely need machinery, as much as you can afford, or you will wear yourself out using a fork!
I didn't mention the front loader and back box on the Siromer, but if you go that way, then it's best to get the hydraulics from the start - ours had to be retrofitted which involved a long day down near Blackpool to get one added. Both are invaluable. We took over 20 years to get all the attachments we use for the Siromer, just finding what we needed as we went along, and as we could afford it. For a trailer, we have one very small one which fits behind a grass cutter, and we also have a sheep trailer which can fit onto a tractor and a land Rover as well as the car, and is used for a whole lot more than sheep - logs, hedge trimmings, manure, hay bales at haymaking time, fetching in feed and compost, sand, stobs for fencing, anything and everything we need which won't fit inside some other vehicle. A trailer is essential

so get one that's big enough, or get two, one small for the walled garden and one larger for everything else (our small one cost very little)