Yep, she(he) was definitely trading. Ultimately though, they should pay because they increased her betting limits after she'd lost heavily. That's what is so poor about this case.Whilst getting gubbed by bookies is a 'one rule for them' annoyance and not disputing B365 should pay up the 54K there are a few bits of this case that give the game away.
The 'she' bit. 99 times out of 100, it's a bloke assuming his other halves identity after he has previously been restricted
He's almost certainly trading. Anyone who has been around the game for a while knows that betting more than £50 at best price (unless you work for the RP) on a regular basis is a trip to the restricted bin. Trying to nick 1/2 a point for 7K on betfair is never going end well.
As a punter there is an element of be careful what you wish for. If legislation came in that bookies must accept £50 bets from everyone and anyone, take a look at Sunbets to see the type of prices that would be on offer. I've no idea what the answer is but I just accept backing at fancy prices is a small stakes (<£50) otherwise it's off to the exchanges.
A couple of other things - if you want value on long prices, ALWAYS head to the exchanges. It's not uncommon to get 120 (less commission) at the exchange where a bookie might offer 33/1 or even 25/1! The bookies are more competitive with favourites though, and often come with good offers like moneyback if 2nd to the SP favourite, that sort of thing.
And Sunbets prices are indeed toilet for the horses, but their football prices are quite reasonable.