Chris, thanks for that, I won't be doing it myself but must admit was coming down on the side of dinatrol.
Clive, thanks, had a peek at their website but it's a bit far for us to go. most are saying a two day job cleaning and more importantly drying then treating so a hastle to go that far. As we're planning to keep her a long while we thought best to get her done early though and LR will only do a quick spray round and not go deep enough for what we need!