Thanks Sloaken - appreciate the length you have gone to here. Some useful suggestions but a few clarifications on my brief:
1. It's an in life product that's been in the market for a number of years, no big recent development on it from what I see.
2. I'm not responsible for the code - I work with the team that is but because it's in life don't think there is a dedicated code expert for this at the moment.
3. Boss is very aware and supportive - he laid his cards on the table when he offered me the job. They are in the same boat as they were parachuted in to takeover due to previous manager moving on.