I'm a little confused as to why you would ask a solicitor for financial advice. Maybe you are slightly unclear as to what HSBC are asking for.
If you need an independant financial advisor, try a quick Google search for the Personal Investment Authority. I believe they are the industry regulator, and should be able to direct you to a local IFA.
If your parents are willing to have their house used as a guarantee for the HSBC loan, have you considered a remortgage instead? It is likely that the house is worth considerably more than your parents purchased it for (unless you have only just moved in), and a substantial amount of capital can be released from a remortgage, possibly even enough to cover your full training costs. You will also be able to benefit from more favourable interest rates and repayment terms than HSBC will ever offer for the Professional Studies loan, or whatever they call it these days.
I would ask your IFA to consider both options and make a recommendation on the best one for you.