We are currently investigating this. I would suggest that you look at the Charity Commission web page. They have some useful stuff all about regsitering and the benefits. You can also search to see what Bands are registered so it may give you someone to target for experience. www.charity-commission.gov.uk
I am 100% certain that my band, B+R, have charity status. I'm not clued up in its significance but suggest that you go to the band web site and contact the band chairman, Derek Rawlinson via that page and he may offer you some advice and facts on how to attain charity status and what your band needs to do.
We've been looking at this as well. Are there any bands out there who are registered that have a constitution on-line that we can look at?
The main advantages to us if we were to become a charity as far as I can see is zero rated business rates for our bandroom and it would open doors to obtain grants from several charitable trusts who only fund registered charities.
I've been in a couple of bands that were registered charities. You have to submit certain info to the Charities Commission (yearly?) but it shouldn't be any hassle if your accounts and admin are up to date anyway. The main benefit to the band was a nice tax-free earner on any subs paid by standing order - definitely worth it just for that!