Question: how many mbtc in 1 btc?
Answer: mBTC stands for the SI unit Millibit which is 1 thousandth of a bitcoin, or 0.001. So you have 100 mBTC * 0.001 BTC, or 0.1 BTC. The price of 1 BTC at the time of this writing on Coinbase in GBP is £5,485.21 to 1 BTC.