So hypothetically speaking, if I bought some coins today and the the trend went through the roof again and I wanted to sell my coins am I right in saying I can only sell what people want to buy off me?
Right.
Because for example in the share market if you want to sell you can just do it at any point in time and it is a guaranteed sale I believe (think that's right)
Wrong. You can only sell shares if there is a willing buyer for the shares you want to sell.
but with bitcoins are you restricted to what you can sell depending on the demand from buyers?
Remember that demand from buyers is what sets the price in the first place. If the price is going up, that means that people are willing to buy it for higher prices (in fact, that's the
only thing it means).