I bought £100 of bitcoins through Coinify on 4th Jan 2017
Not sure whether to buy a few more or cash them in. Looking at some technical stats, it's showing bullish.
Excuse me if my assumption are wrong or out of place, but given you only invested £100 to invest with and now have not too far short of £1k I can imagine that your investment now wouldn't be substantially bigger than your initial £100 investment.
Given that I wouldn't bother to invest another £100 or so on top of a holding which is now much larger.