First of all condolences on a tough situation, and I admire your attitude "I need to sort out my finances"
You say you spoke to the bank and they wont give you a mortgage. I assume that this is the same bank that gave you the personal loan.
Of course they won't give you a mortgage, what advantage would that be for them. At the moment they have a performing loan at 7.7% (rough caln). Why give you a mortgage at 4.5% or less.
Suggestion 1. Try other banks, have you a banking relationship with them. Where is the salary going from you job. If it is the original bank I suggest you change now. If you can prove that you have been servicing a loan at €900 a month and paying rent for four years, you must a reasonable prospect for another bank. Although the valuation of the site will be an issue.
My advice on how to approach another bank, is to walk in off the street and discuss with a mortgage advisor or manager in a bank. If you get negative feedback walk away, and try another bank or even another branch of the same bank. If no file is sent to the underwriter you can start from fresh with a different person from the same bank. Youwill learn from their questions and attitude what you need to get them to offer a mortgage.
Suggestion 2. Stop paying the repayments on the loan. Now instead of having a performing loan at 7.7%, the bank has a problem. Their first response will be to threaten you, and you will need to be prepared to live with that. You could counter threaten with an accusation of miss-selling. Eventually they will have to make some kind of offer. There is little benefit to them in taking you to court unless the can get something from you. Remember though it will cost them little to threaten. Keep putting the money aside as of course interest will keep clocking up.
I have personal experience of suggestion 2. The circumstances were a little different but they made me an offer that I could meet and in just a few more years I will have put it behind me.
While I was dealing with a manager from the bank a friend a bank employee was advising me privately. I was told that the managers dealing with problem loans have much bigger issues than mine (€200k). If he gets a half decent proposal he can call that a success and move on.
I hadn't made any payments on the loan for nearly two years and my file had been moved from the original relationship manager to someone dealing with problem loans. In fairness they didn't threaten, just kept ringing me up and asking "what are we going to do about this", to which I would reply "I don't know, moneys tight". I never paid anything until I received a revised loan offer which I could cope with.
Suggestion 3 Sell the site. You wont be able to get a mortgage of course because you wont have any security, but your problem will be halved.
Good luck and don't let this cripple your spirit, all this is only a small part of who you are. While it is trite it is also true to say, its only money. Your health is more important