Something I find strange about the UK punting scene is that, there is talk of a good game when it comes to hygiene but it isn't actually practised well.
In SE Asia, the SOP is a shower with the WG before the session (no excuses) and, among the better providers, antibacterial mouthwash. Here, you more or less take her word that she'd sanitized.
Maybe we punters should start demanding for the same services? That said, 2 person showering in a bathtub could be quite hazardous (Wetrooms seem to be still relatively uncommon)
so methinks watching her gargle is the only option
But to answer the question, yes I'd probably be put off punting altogether if I caught something nasty