SteveF is correct especially with regard to changes in advance, but point (2) is slightly misleading.

I was also affected by the ash cloud on BA tickets booked through Expedia. BA handled all the compensation matters after the event, not expedia.

The TA mess comes when it's an all-inclusive booking (so flight & hotels together).

What's your upside - 4,000 VS miles? So about £50? I might be tempted, given the very small risk you take in going through lastminute.com