honestly it will be difficult, if you wish to spend a fee quid to check, employ a local architect or arch tech to assess your situation and prepare a brief document on your behalf outlining your local needs/ sf1 form, be honest and expect the worst. I do this type of work regularly and it can be really heart breaking where couples get their hopes up. simply put A3 zoning is reserved for farming & associated rural uses with the 7 year rule and your existing house ownership messing you up (btw do you work locally?).