If you try and do a cost/benefit analysis of "is it a good idea to spend all this money to be a pilot" then the answer will generally be no, as the figures just dont stack up and many people fall by the wayside.
On the other hand in my experience the people who plug away and are persistent generally make it, it's not a career for people who are not giving 100%
Becoming an instructor first is the low risk option to becoming a pilot in the UK, you should pick up work if you make yourself available. So I also think you are asking the wrong question, you should be asking "how much risk am I prepared to take" and if the answer is "not much" then give up now.