Thomas Cook Airlines are offering direct flights from Glasgow to Las Vagas for £299 return.

The outward bound flights depart on either:
2nd or 9th November

The return flights depart on either:
9th or 16th November
(You can mix or match dates to suit, depending on availability)

So you can choose a one or two week stay.

The flights are all operated by Thomas Cooks newly refurbished, A330-200 aircraft. Which look better than economy on BA and Virgin, they have installed brand new touchscreen in-flight enterainment, increased the size of the seats by reducing the number of seats from 9 to 8 across and leg room is good too!
Here's a video of the nwly refurbed planes:
https://www.youtube.com/watch?v=69k54dlAHJU

These flights are so cheap, you could look at using it as launch pad to visit California. For example hire a car and visit LA and then stay in Las Vegas for a few days before flying home.

I am finding onward flights on SkyScanner to LA and San Fran for £50-60.

Hotels in Las Vegas are dirt cheap, I am finding 3-4 star hotels just off the strip for less than £100 per week. Try looking using Trivago or SkyScanner Hotels to locate a hotel at a cheap price that suits.
(No these are not sleazy motels.)