On the subject of porro/roof inexpensive alternatives, my favourite budget binocular in terms of value for low price is indeed a porro: the Kowa YF 8x30. Well within your initial budget (I've seen them way below 100 GBP) and stunning little performer for the price. As a bonus, is a really handy and nimble binocular that your kids could use (it has a ver narrow minimal interpupilary distance).
I have a pair, have given several as present and never ceases to amaze me. One to definitely look at.
I have a pair, have given several as present and never ceases to amaze me. One to definitely look at.