LastMinute.com review: Booking flights

On 23.9.23 booked 4 return flights from Manchester to Orlando. I selected our desired departure date of 6.8.24 and hit search. At this point I noted that I'd searched packages where I only wanted flights, so I hit the flight only button. I was happy with the search results so went ahead with the booking. On reviewing the details I noted that the departure date was showing as 7.8.24.

I immediately requested a change to the 6th which has been caried out but at a cost of £105. The following day I received a phone call from LM to inform me that due to the cost of the flights increasing the actual cost was going the be £365.

I have a number of issues with this;

1. on revisiting LM.com I note that when a search for a package deal is changed to flight only the date changed, it was NOT my error that had caused this in the first instance

2. On checking the same flights after receiving the call I note that the price hadn't increased, it was EXACTLY the same as the previous day when I originally booked

3. legislation dictates that I am allowed a cooling off period of 24 hours when booking flights in the UK in which I am able to make amendments or cancel without any charge, so why has this not been adhered to?