If you do a dummy booking on Alamo.com it gives you the option to add insurance(CDW) you have none included in your quote, its $23.99/day, for 15 days(I think you have 15 days rental?) that will be $359.85
Add that to your quote of $749.33 = $1109.18 = £706 and I am still not sure if you require Extended Protection (EP) if you do thats another $186.60(£119)
Your total would be minimum £706 max £825 working on exchange rate of £1.57
USrentacar(1st site I checked) would be £652 100% certain everything is included. £724 if you want additional drivers and a tank of gas included.
Info on Alamo CDW
https://www.alamo.com/retrieveChargeItemDetail.do?category=ADI&subCat=CDW1#CDW1
And EP
https://www.alamo.com/retrieveChargeItemDetail.do?category=ADI&subCat=EP#EP
The insurance is added at the extras page, looks like this:
0 1 2 Booster Seat ($9.99/Day; $49.95/Max Amt) $0.00
0 1 Greenhouse Gas Emissions Offset ($1.25/Rental) $0.00
0 1 2 Infant Seat ($9.99/Day; $49.95/Max Amt) $0.00
0 1 2 Child/toddler Seat ($9.99/Day; $49.95/Max Amt) $0.00
0 1 2 Gps Navigation Device ($11.99/Day; $69.65/Week; $179.99/Max Amt) $0.00
Collision Damage Waiver Full ($23.99/Day) $0.00
Extended Protection ($12.44/Day) $0.00
Roadside Plus ($4.99/Day) $0.00
Return Fuel at any level ($2.79/gal) $0.00