The Ice-Cream Lady
Until the 1980s, a traditional British cinema show (sorry; wrong band...) began with a secondary film, then an interval, accompanied by adverts and trailers, then the main feature. During the interval, the usherette would stand somewhere in the aisle, selling drinks and, primarily, ice cream, from a tray. This is the 'ice-cream lady'. Chloe Irving suggested that she may be a reference to another feature of British society, the ice cream van, mentioned simply to reinforce the idea that Ronnie is just an ordinary British bloke, but whereas a van doesn't fit the context of a viewing room, the cinema usherette certainly does.
Chloe further suggests that the ice cream lady may be Ronnie's mother, and these lines are a reference to Ronnie's birth - his mother 'wet her drawers' (when her waters broke?) in order to let Ronnie into the Play (life). There is indeed a secondary meaning to the word 'see' in UK dialect: to escort, so the idea is very credible.
The interpretation that the ice-cream lady may refer to Ronnie's mother is a popular one, which a number of contributors have proposed, and it is indeed worth mentioning. However, I suspect the 'real' meaning is simpler: that the usherette may have (metaphorically) wet herself laughing when she saw the film of Ronnie's life. This is the more usual connotation of the slang phrase 'to wet one's drawers (pants)', so I'd suggest this is the most obvious surface meaning to the phrase.
It's worth remembering that the ice-cream lady had previously appeared in the lyrics of the Chateau material, where the reference to a theatre usherette is even clearer:
The interval will last until the ice-cream lady melts away.
A truism in one sense; the interval will be prolonged until the queue of people waiting to buy ice cream has gone, and the usherette disappears or melts away as the lights go down again.
Taken in the context of the Play, ice cream could be a metaphor for fleeting pleasures that melt away all too soon. To stretch it even further; a pleasant love affair might be an 'interval' in a busy life, before the couple split up, the woman leaves (melts away) and the concerns of career, money, status, etc. reassert themselves.
A wonderful string of meaning from a single elegant phrase; all lost when the Chateau material was abandoned. Perhaps Ian was so enamoured with the ideas that he reinserted an echo of that line into the finished album lyrics, almost as a shorthand reference to the deeper meanings of the earlier version.
It's possible that taken alone, without this back-reference, the line is just a nice image setting the scene of the viewing room, without any deep meaning of its own.