The Ninja 250 is what woman start out on in the U.S.A..
and that's why people die young...
in the UK things are a little different...
to start with you have to take a basic course called a CBT.
If you have a car license as well that'll let you ride a moped (50cc) forever, no questions asked.
it'll also let you ride any bike up to 125 (there is a power restriction as well that means that bikes such as the CBR125R have to be restricted),
you can ride them on any road (except motorways) with learner plates.
if you do that for two years without taking a full test, then you have to retake the basic training and can continue to ride up to 125 with L plates.
if you take the full test there are two ways to do it.
if you're under 21 then you have to take the A1 test, that means you have to take a full test with an examiner trailing you, on a 125 bike for half an hour and complete a set route with a series of set manoeuvres, if you pass you get your A1 license and can ride any bike upto a 250 for 2 years, aftre that point you;re unrestricted and able to ride anything you like.
if you're over 21 then you can go the A1 route with the same 2 year power/size restriction, or you can opt to take an A2 test.
which is the same test route same manoeuvres etc but on a 500cc bike.
if you pass that test you can ride whatever you like straight away.
and regards the little ninja 250, they are plenty good enough to pretty much keep up with bigger bikes because they are much lighter.
and because they are lighter if you're on a twisty road and a decent rider you'll be able to get down the road faster than a guy on a much bigger and more powerful (yet less manoeuvrable bike).
the little ninjas are quite good... and if you look at power to weight ratios then they look absolutely amazing!
AXA just quoted me £4k for a CBR 125R 124cc...
go to bennets and see what their best quote is, (they are normally pretty good for learners).
the other advice that I have is this.
don't buy a CBR125R,
they are lovely bikes, but they are a pain in the arse, they are high performance bikes, and need constant care.
they are above the legal power limit that you're allowed on a cbt/learner license so you'll have to get it restricted.
they are damned expansive to buy.
easy to steal and thus expensive to insure.
honestly I'd recommend anyone to go the same route that I went.
buy a cheap Chinese bike from ebay direct from an importer and unregistered, (I got a lifan bike). (price £600) (including delivery in the crate it shipped in to my door).
Get insurance on the frame number (bennets will be able to find you someone who will insure on this rather than the registration) (price £180)
go to the DVLA with the import documents and buy a registration (£20) and tax for the first year (£15) (total price £35)
call your insurance and have them add the reg number to the insurance. (£20 to amend the details) -you can ignore that until the renewal if you want so that it doesn't cost you anything.
600 for bike
100 for CBT
35 for tax
180 for insurance
and I think it was about £10 to get a number plate made
total price to start riding less than a grand (or less than a quarter of what you're being charged for insurance).
plus, you've got a brand new bike, so you only have to tax it, there is no MOT required for three years.
so your total cost for riding the bike for three years is £900 for the bike and insurance then £15 a year tax and £150 or thereabouts insurance for the next two years. (still a quarter of your 1 years insurance but you get three years of use!)
at which point you've had three years decent service out the bike, and you can sell it on ebay for about £50.
the only downside to that approach is.
the bike comes in a crate, so you have to put the front wheel on yourself, and attach the handle bars, (as they are not attached to save space).
for your own piece of mind you should also go around the bike securing all the nuts and bolts with locktite. (which is what you'd be paying the dealer to do if you.
Some people doubt the quality of the Chinese made bikes, all I'm going to say is that I rode mine for three years and never had any real problems, but I have read some real horror stories.