Are you trading the major pairs? Who is your broker buddy?
Saw this post but couldn't answer at the time and if gets more than 24 hrs old and didn't write the name of the thread then the way the posts are set up there is no way of finding it again so thanks @gaar for refreshing it.
Couple of points;
a fixed spread broker won't have huge out of hours spreads but might not have the lowest average spreads.
Orders get filled on live depending on volatility, pending orders first, market orders last, so a pending order is more likely to get filled. Brokers have a degree of tolerance before they fail to fill if price jumps over your pending order price, or requote if it's an at market order.
The spread is higher out of hours because the broker's biggest liquidity providers close at end of US market (10pm London) and the broker needs to reach out to more expensive providers which is why you may see a spike in prices at 10pm London time.
Some broker's demo are better than others though never same as live, some will fail to fill or requote similar to live but as said, if price has moved very far from your order price the broker should cancel rather than fill at a far worse price, some brokers are better than others.
When trialling live always start with the minimum amount lot size (price per point) the broker will allow and see how it goes.