Like any broker / lender, they will have a legal obligation to treat you in an ethical way. Is it a secured (homeowner) or unsecured loan that you are seeking?
If unsecured, no upfront fees and completion period of around 2 weeks - if accepted. Min. loan is �500, Max. loan is usually �25k
If secured, again no upfront fees and a completion period of around 2-3 weeks, depending on the amount. Min. loan �3k, max. loan 125% of your home value (less your mortgage balance).
Do not take Payment protection (unless you feel that you need it) and feel free to haggle any fee then shop around for the best deal for YOU, not them.
It is unlawful to charge upfront fees of more than �5 on loans, so most brokers do not bother.
If you are seeking a homeowner loan, try Refinance UK on 0800 8349 1000 - they are very good!
I find service levels are one of the most important aspect of any transaction of this nature and that is usually down to the mood of the person who takes your call. If you are not happy at any point, make the Manager / Director politely aware of your unhappiness and then withdraw your custom - thats what I would do.
You will be amazed how much effort they may make to win you back. If they dont, then you made the right move!
Hope that helps, good luck