@ tomorton, first you make a lot of excellent posts, and I do very well know that and respect that.
However, with respect, you've made a questionable point here.
"You can't adjust your guaranteed stop level, so if your GBP/USD long goes straight up from your entry, your guaranteed stop can be left stranded hundreds of pips below, you've already paid for it and you're only allowed one per position."
What you said used to be true, but you should note that in recent years, all guaranteed stops with IG and the others with whom I've accounts, *can* be amended, as long as the relative minimum stop distance is maintained. That is, a guaranteed stop definitely nowadays *can* be amended after a bet/trade is opened, and is well worth doing if e.g., you've a trailing strategy.
To the OP
I've been spreadbetting since before the 2's. And I can assure you for the last decade, spread bet firms have been behaving professionally and fairly. Nevertheless, the reviews you have been reading may seem like BS to people who've not had earlier experience, but to a few like myself, I can assure you that things weren't always as smoothly nor fairly run, in earlier times.
It was true, *over* a decade ago, that certain spreadbet firms used to (do such unheard of practises nowadays as) freeze your platform, place phantom trades on your account, prevent you from logging in etc. etc, etc., *if* you made one too many winning bets. I know this is true as I experienced same from certain firms in the early years for myself. The forums of old were literally awash with such complaints in the early days . OTOH, the people who are saying that such reviews are nonsense, are *relatively* right, i.e., BUT *only* as far as today's firms are concerned. When it came to the s/b industry at the turn of the century, things were very different indeed.
The reviews you see, weren't just written by losers with sour grapes to bear, I can assure you! Sure, some of course were written by losers etc., but not all - by any means.
Anyway, please don't worry about such factors when reading reviews now, because such complaints really don't apply any more. There is too much competition and openness in the industry, that no s/b firm worth its esteemed public status would be bothered trying to make any client lose, these days - no matter how well he is doing. What's more, as 'Highburyfx' would tell you, most s/b firms would actually lay any consistently winning spreadbetter's bets on the underlying itself, if they ever made it to the elite and prized "A book" status.
Just concentrate on what a s/b firm has to offer - range of instruments, tightness of spreads and competitive margins - and you'll be good to go. HTH