Hi Petrol1 and welcome to the group
Nice to hear you're thinking of an aNTy for your commuting. A wealth of info available on here to help make your choice, and keep her in top shape.
Fuel consumption, unless your daily commute means getting stuck in lots of traffic, you should get more than 60mpg, unless your right wrist gets a little too "active".
Servicing - many places to get your bits from. Many of us use WeMoto (look here for other links)
www.ntvhonda.proboards.com/index.cgi?board=links&action=display&thread=27Just to buy the parts will cost a few bob (but no more than any other bike/car), but it's worth getting done and you know all is well.
Unless you're very happy about previous service history, I would recommend changing the coolant and rear bevel oil too. Brake Fluid isn't a bad idea either (more later). The prices I mention later are indicative and don't include postage.
If you don't have a Haynes Manual for the bike, that is worth having too. There are some quirks to working on aNTy that Mssrs Haynes help explain, although Franklin is building up a library of work on his pride and join. You will find "fun" having to half strip the bike at times to do simple maintenance, like tappet adjustment! These are all jobs that seem frustrating at the time, but worthwhile when they're done. Always allow plenty of time when you're doing simple jobs.
Front Brake, nothing much to add to that already suggested. Even fully loaded, the front brake is pretty good, especially for a single disk.
Check the pad thickness and condition of the disk.
Unless the pads look very new, it's worth changing at a cost of around £20 and then again, you know they're not glazed, contaminated etc.
Flush the fluid through and retry
Stainless braided hoses do make a difference, but you will be looking at £30 for that, plus (I recommend) new banjos and washers.
There are two pistons in the front caliper, which is a floating type so you might want to check that the pins are clean, not worn and sliding OK. If you feel handy with a toolbox and lucky (that the seals etc are in good order), a quick strip of the front caliper will do no harm, but if the seals are getting worn, you may end up having to splash out for those too (£15 for a set)
You mention "clip on" Handlebars and they're too low. This is worth exploring to ensure you know what you're buying.
Are the speedo and rev counter the same size? If so, you should have a top yoke with clamps for conventional handlebars and any normal diameter bars will fit. Your bike will be a 650 and all is well?
However, be very careful about putting any new bars on, especially higher than a conventional height as the cables for throttle and choke are not very forgiving.
If the speedo is bigger than the rev counter, the top yoke will have a bolt on arrangement for the handlebars, you can only put on Honda OEM bars, the bike is a 600 Revere.
Are your clip ons clipped to the fork stanchions? can you describe the top yoke?
