Wow, what do you expect for £750, brand new!
Look at it. Got the 127 tooth metric gear, that is expensive. Look at the tumbler reverse gears, are the teeth still as wide as the gaps, so not worn. Screw the two chucks on, not tight, but enough to be able to pull on them to see if headstock wear. Rotate the chucks slowly and feel for any graunching, and in back gear.
Move the cross slide, press a finger tip against the slide whilst rocking the feedscrew, as you increase the amount of movement then wait until your finger tip can feel the slide moving. Finger tips are extremelty sensitive for this. Repeat on top slide, but it would normally be much less worn. Rock the carriage with the handwheel, there will be at least 10 or 20 degrees of slop, it is a gear into a rack, but feel if it is graunchy up near the headstock compared with the other end.
Power it up if possible, how noisy is it in all speeds, but just one in high gear and one in backgear will tell you most of what you want. Are you familiar with the noise a lathe makes at 700rpm? Pretty noisy, but not ear muff noisy. Put the feeds in and out, forward and reverse, noisy?
Does the tailstock barrel move smoothly?
Look at the bed in front of the headstock, how many times has the chuck been dropped on it. The bed uses raised Vee ways, look at the state of them. Look for signs that they have hacksawed stuff off in the chuck and overshot and hit the bed. Hopefully hardened so any wear in the saddle which can be scraped out.
Just stand back and look at it, is it twisted, are the cabinet panels all straight and undented.
In the end you have got most of a lathe, two new chucks but probably not Burnerd, the cabinet is a lot of money, and making a good bench isn't so easy.
If you can run it and sounds ok then easily worth that money. If you can't run it then have to look at the pulleys and motor, have a good sniff, if burnt out then the smell lingers for ages. My guess is that it was used for turning down commutators or something like that, certainly not model engineering, hence the grubby look. Boxfords are like South Bends, good basic lathes.