What to do at 1930 on a Sunday, when the neighbours are playing loud music?
Er, . . .dance?
Seriously, 7.30pm (on any day of the week) is hardly 'late'. If you're trying to get your toddlers to sleep (and you get on well with your neighbours) it wouldn't be unreasonable to politely request that they turn the music down (while explaining the circumstances). However, any 'formal' complaint would seem to be unreasonable
Everybody has a different view about noise pollution. My own feeling is that it wouldn't be unreasonable if my neighbours had all-night parties (preventing me from getting any sleep at all) once or twice per month. (I'd certainly not consider complaining and I'd vehemently take the side of the party-animals if other neighbours complained).
However, if your daughter is being subjected to
persistent noise problems (at
genuinely unreasonable times), this might help:
http://www.direct.gov.uk/en/HomeAndCommunity/W hereYouLive/NoiseNuisanceAndLitter/DG_10029682
Chris