Saracen can probably answer this better, but I would go and get some profesional advice about this s soon as possible. £3000 a year is significant enough that could get you into a lot of trouble and be costly if you don't.
As for using your employers software to do work for someone else, especially if they are in he smae line of business, could be cause for disiplinary action if you were found out.
And as it's your employers software are you also using your employers computer? Again that might not go down well.