Washy, the visa application would have asked for the planned travel date. What was that?

The temp vignette in her passport is valid for 30 days from the date stated in the application as the intended travel That vignette will be her proof of entitlement for UK entry but only within the stated 30 day period.
If she doesn't travel to the UK within the indicated 30 day period then yes, she'll need to apply for a new 30 day visa as the original will be expired.
Yes, as you say there's a fee for this around the cost you mentioned

Your wife will get a letter explaining everything including how she must collect her full BRP when she arrives in
UK. This needs to be collected within 10 days of arrival and from the Post Office indicated in her letter.

Failure to collect without giving notice is pretty serious so try all you can to follow the instructions in the letter.

Hope that helps