FSA timescale guidelines on complaints?

You mean the 'FOS'. It is eight weeks from the date of complaint

Usually the 'firm' must acknowledge your complaint within one week

They must must then write to by four weeks unless they have decided and notified you by then

After eight weeks, they run out of time and you can involve the FOS

FOS first looks at your complaint to see if fits within their rules - a large proportion won't be and they will write to the complainant to explain why not

If the complaint is 'allowed' they then take a further look and ask the firm if it wishes to settle part (or all) of your claim. This allows them to wrap up most complaints they do allow to proceed without more time and money involved....

Assuming the firm offers no redress - or they do and their offer is rejected as inadequate by the complainant the FOS must then formally investigate and decide. Their decision is only binding on the firm, however, and the complainant is free to go to court if they wish. However, the FOS decision will essentially reflect the principles a court would follow so it is nearly always going to be the 'final' decision anyway.

Note that only 1% of complaints make it to the third stage above. They complain that they are kept too busy but in reailty they filter complaints right down to the the real 'hard cases'...