he has passed away and the farm and house is left to siblings equally which is totally unworkable they are trying to push me to take the house and they want the land which is more valuable
With this you are not in a situation where you can just hold out indefinitely.
When you say your brother gave you the site, did he do a full legal transfer? If so, are the beneficiaries of your brother's estate proposing a land swap (where they will effectively buy your plot of land and sell you the plot with the house on it)?
Given the beneficiaries' approach, I suspect the plot of land you're occupying was part of your brother's estate and you don't own it. If that is the case you would be best advised to engage with them and try to work something out.
In most cases, a plot of land in the country with a house on it will be more valuable than an equivalent size plot without. Just look on Daft for your area and you'll most likely see plots even with derelict properties on sale for multiples of what agricultural land or clear sites are going for. It is far more difficult now to get permission for a one-off home in the country, and I suspect it is very unlikely that a 13 year old cabin will meet the requirement to be granted retention.
If you can't work something out with the beneficiaries, be aware that they are perfectly entitled to sell the land, and with that will go your electricity supply. You will not get a separate supply installed to the cabin without planning and RECI certification of your full electrical installation.
Your first action should be to confirm what, if any, land you own. If you own none, your options will be limited to what the beneficiaries offer, if anything.
If you confirm you do own the plot of land your cabin is on, then speak to a planning consultant (not in the employment of the LA) who is very familiar with what your LA will look for in considering a potential planning application. They will either outline the work that will be required, or tell you not to waste any money chasing an impossible dream.