First of all I would leave it another couple of days in case the post is slow (if you are expecting a cheque or postal order) and BACS transfers normally take 5 working
days to clear (I'll ignore the Faster Payments System) so that would be, what, Thursday this week?.
I presume that you can't call into their office? It is often easier to deal with things in person (and you may even be able to walk out with a cheque).
When you threatened legal action - did you give them a date to refund the money by before you took legal action? Did you say what sort of legal action you were going to take perhaps by quoting the www.moneyclaim.gov.uk
website (which often is a way to show that this wasn't just an off hand comment and you are being serious). Can you show / prove that the group received your email (normally its best to send a recorded signed for letter but if they replied to your email I'm guessing (no experience here) that the reply with your message on it can be taken as proof of receipt).
Once this date is past and you have left it a few more days for monies to clear, you are well within your rights to start the process (£35 on http://www.moneyclaim.gov.uk
when claiming for £450 - see http://hmctsformfinder.justice.gov.u...rms/ex50_e.pdf
for the scale) but the process costs more money the further you need to take it. For example:
£40 to get the case on the "Small Claims Track"
£55 for a hearing fee
then presuming you win, £40 to enforce the judgement in a county court
then more if you still need to use baliffs, etc
Once you win the case though - you can also claim all that money back from them.
Going legal doesn't really cost that much - but it a time consuming process. Calling in, preferably after having booked an appointment (so they can't turn you away) would be much quicker - but I don't know if that if feasible for you. It is up to you how much time you want to use up in the chase.