I work for a charity, so have a bit of inside knowledge on this type of stuff.
First up, in my job I see a *lot* of requests for money and goods. RR's letter is excellent
- it says what's needed right up front. Nothing annoys me more than having to read a great long spiel of stuff I already know or could easily find out with a vague and pathetic "Please give us your support" right at the end (What exactly do you need and what's the benefits? - that's what funders want to know.)
Where the letter could be improved is through putting in some 'happy stuff'. Of course you need to show the need. But the request also needs an example of how their contribution might help (and there's enough wonderful stories on here of how kitties have survived and been rehabilitated from horrible circumstances). With apologies to those with charity experience, but for the benefit of those who don't: the 'after' story is what we call an outcome. ALL donors look for outcomes. They may not work directly with the cats - you do. Share the success as well as the heartache.
Second, there are many advantages to being a registered charity. It gives you credibility as there are certain legal requirements that have to be met in terms of financial reporting etc (not that stringent or costly at the kind of levels of money you guys would be looking at). Many charitable trusts are legally restricted by their trust deed to funding only registered charities. So even if they want to help, they can't. Many businesses have a policy of only giving to registered charities. Another advantage of registration is that you can reclaim Gift Aid from taxpayer contributions.
Yes, you have to have a committee (minimum three trustees) and constitution. http://www.volresource.org.uk/
is very helpful for people looking at setting up a charity - and far friendlier than the Charity Commission's website, although you will need to go there for registration documents etc. (NB I have no connection with Volresource except that I find it useful).
There are so many individual rescuers out there - why not get together to set up a charity? There is nothing to say that you all have to live in the same town. And as you are all volunteers, you can all be trustees (Trustees may NOT draw a salary but MAY reclaim expenses associated with their charitable work). Meetings don't have to be that frequent - once every three months should be ample. Surely some of you must live within close enough distances to make that reasonable?
Free (pro bono) legal advice and accountancy services are often available - talk to your local volunteer bureau as local solicitors or accountants may be registered as interested in donating their time to local charities.