Thanks for the reply. Looks like I'm going to have to change tactics  

Yea, usually the price drops before it is filled

sorry I got it wrong, I meant 'higher'. Gdax won't let me sell at a lower price than the latest. I assumed that's normal?

There's a pretty hefty charge for market orders. I sell at the last available price, which should be the fastest. If I sold at lower then it would take longer as I would have to wait for the price to drop to sell.

I trade mostly with GDAX and for some reason doing a limit sell or buy takes ages most of the time. I'm talking 15/20 minutes in which I have to constantly cancel and re-instate the trade so that it stays at the last price. This is annoying because I try to come out just before a dip and by the time the transfer gets processed its usually too late and well into the dip. When I use Bittrex it usually takes seconds. Why are GDAX trades so slow? anyone else experiencing this? I trade in euros as the dollar wallet is not available here.

Thanks for the replies. I think I am overthinking this way too much. I'm just going to hold and see what happens.

I am planning to sell all of my bitcoin and segwit following the upcoming fork. Judging by the last fork, bitcoin lost 200 dollars within 9 minutes and then carried on going down before rising again.
With regards to selling, GDAX have stated that all transactions will be frozen until they are certain that it is safe. This means that we don't know if we will be able to sell within those 9 minutes right? Considering that segwit will more than likely fall too, what is the best option?

Is it worth the risk just to get free segwit or should I just take my bitcoin out now and wait for the fork to happen before buying bitcoin when it is cheaper? The other issue is that making a 'limit sell' (to avoid fees) will surely be virtually impossible during the minutes following the fork considering the huge price fluctuation? So would a market sell be better (paying the fee)?

What are your thoughts?