Hi Matt,
Cant offer much advice, as like you, i am very new to this subject, and also like you, i have limited funds available to me!
Do you use www.the-saleroom.com/en-gb ? It searches all UK auctions, and once registered you can set up email alerts for keywords (eg "Katana").
Downside - unless the auction house happens to be near you, you generally have quite rubbish photos to go on, and poor descriptions. Plus all said and done, fees are generally 25-32% ON TOP of the hammer price.
I have two swords, both bought via this auction site. Each sword came to ~£1,300 once fees were added.
The first is a bit tatty - but at least appears to be old (1500s/1600s)
http://www.militaria.co.za/nmb/topic/21188-help-with-signature-translation-ww2-sword/
The second is much more recent (1942) but absolutely immaculate, and from a known (WW2) smith thats reasonably well respected.
http://www.militaria.co.za/nmb/topic/21367-my-1942-munetoshi/
I feel like i have paid over the odds for the "old" sword, but maybe got a bargain on the "new" sword, so possibly its balanced out! (thats "man maths" at work there).
Mind you, if/when i see another sword, i dont think i will be any better qualified to know if its legit. I will rely on the kind chaps on here to guide me.
I have chatted via PM to a few other UK guys, so dont hesitate to drop them a line.
And if you are ever passing through Berkshire, you are welcome to have a look at my pair. (ooh matron!)