Interesting research you are doing here firehose. There is a danger in this though - That you will draw up a huge list of things which will guarantee your account never to get gubbed; but it will also severely limit the offers you do and the profit you can extract from the free bets.
but let's see.....
How long did you manage to keep your account open? - around 8 months I think.
Did you do accumulators? - Yes, occasionally.
Did you play on their casino games as mentioned by Jon? - Yes
What was your ratio of mug bets to free offer bets? - I tried to make every other bet a mug bet.
Did you bet on a 'favourite' football team or was it a different team each week? - Different teams.
Did you watch the horse race/bet event when it was being streamed from the website? - No
Did you ever bet in-game? Occasionally, but only when a free bet required it.
Did you ever bet on their mobile app? Occasionally, but only when a free bet required it.
You may be on to something with those last two as I hadn't considered that before. Thinking back, the only time I did any mobile or in play bets was when a bonus or free bet needed it.