If you are buying a few acres as a lifestyle choice you will probably have to pay over the odds anyway so in my opinion the only professional you need to employ is a good solicitor who will do thorough searches, then read everything yourself to make sure its correct! If it's at auction the price will probably be half / two thirds what they expect it to realise.
I worked for a "rural chartered surveyor" and seeing the amount of money spent just within the surveying circle was shocking. The same parcel of land was "valued" for several clients who all paid three figure sums but fatty in the office only drove out once to look at the place. I have never had land surveyed and have bought and sold loads. Research local land auctioneers previous sales to see what it has made in past auctions, or look up some of the house price websites, i think they list land sales too, so you can get an idea how much it is in the locality.
You will have your limits and know what you can afford and are happy to spend, if the place feels right to you go for it. I would try to avoid anything with a clawback, although would never totally write it off if there are children who may inherit in the future. if there is a clawback try to negotiate a shorter/smaller timespan/percentage.
Of course if you are buying in an area that has been mined in the past get as good a report as you can, then run like hell in the opposite direction! If you can't lift your wellies out of the clay to walk the field, think twice. Avoid flood plains, environment agency has a good flood map so use it hard!!
Look at what others have done round about if you are contemplating putting animal housing on the land, but avoid talking to the planners, their manifesto seems to be a target of 100% rejection of any rural business which seems to go against other things i read from the government/defra etc. Good luck with your buy and enjoy it when you have it, they are not making any more land so its a great thing to have!