Depends a little what you mean by "system". That's to say: not really, but I have my own particular way of putting together information from others' "selections" which I've been developing over the years with limited success.

Yes, I think I probably agree with that. But I was slightly lucky with daytrading, I think. I had probably done a little bit less real work on it than "the average eventually successful trader" does before finding, learning and applying something that genuinely worked.

You're right if you don't have a "ceiling price", yes. Some people don't lay at odds above 7/1 or 5/1 or even 7/2, which obviously limits the number of winners effectively wiped out by a loss. But losers (i.e. winners) seem disproportionately expensive, yes.

There are various different "staking systems" for laying, though. You don't have to "lay to £x" each time.

From my experience, the major problem with laying is that it's even more important than usual to try to do better than starting-price. The difference that this makes over a period of time is almost inevitably the difference between overall loss and overall profit, which makes it more time-consuming and attention-needing than other forms of horse-race betting.