Dam Zio

I am going to buy the properly abroad (Poland) in the shell condition, which means I will need to fit it on my additional cost before I can live in it (fittings like: internal doors, kitchen and bathrooms interiors and furnitures, floor panels, boiler, paintings, ceilings, electric plugs etc. I am UK tax resident, and this will be my 2nd house - I have home in the UK. The purpose of buying the house is that I am going to go back to Poland and live in it - it's not going to be let to someone else. However, my situation may change in 2-3 years and I will need to sell it, so I am trying to be prepared for it. Couple of questions in relation to this situation in terms of GCT. Assuming I will sell the house in 2-3 years without living in it and staying in the UK as tax resident, I have a following questions: 1) As far as I understand I will be liable for GCT for selling this property - correct? 2) I am basic rate tax payer - what will be the rate of GCT for me in the above situation? 3) Are the costs of above improvements (from house shell condition to house liveable state) deductable expenses from GCT? If so, what do I need to claim those expenses - VAT invoices or just bank statements proving the costs are enought? 4) How would my situation change if I would live in this properly for ex. 1 year and then come back to the UK?