does anyone know if there is a possibility to get a house mortgage in UK, but as a 'deposit' use a property located in other European country with value much higher than what would be required for minimal deposit in cash?
Don't know but I highly doubt it.
The bank will only accept collateral that they will possess in the event that the debtor defaults. Europe being a special case where there's a decent chance that a bank could win a case in the EU courts to get the property. However, being that there's a non-zero chance that Brexit will complicate all things involving EU cooperation, I would assume that no bank in the UK would want to make that deal currently (and I doubt they would have in the past, since it's likely just not worth their time to figure out the legality of things involving property in a different country).
The only way to find out is to ask the bank.
As a deposit, no. The deposit is money that you hand over as part of the payment for the house you are buying. The mortgage company pays the rest.
As collateral for the mortgage, maybe. You would have to ask the lender. They would have to be confident that they could sell the other house should you default on the mortgage. Usually, you don't need any additional collateral, as the new house that you are buying provides that.