Self Management

we had this recently too but opted not to self manage.  the concensus was that we had our plots for fun, companionship, exercise etc and not for policing the empty plots and poorly run ones, plus we have had issues with the water supply and there were no figures available for the cost of the water so we stayed as we were.  You need to find out exactly how much everything costs, is your site securely fenced off if not will you at some point become liable for vandalism and have to put fencing up, is the water charged from the LA and how much does it cost (bet its more than £800 per year!), find out why the parish council wants you to self manage because that may well tell you wether or not its a good idea as well!!  IE is there something expensive looming on the doorstep that they want to avoid paying out for.  Take a look at the accounts if you can to find out what they currently fork out for.

Someone on our association committee recently suggested that we should consider going self-managed (we're a council site).  He had done the maths for the rental income (I doubt he was anywhere near the right figure ...) and simply saw lots of ££££.

He got roundly shouted down!  It takes a lot of time, effort, commitment and thick skins to self-manage.  We didn't want that hassle.  It's a totally different level of organisation, accounting etc etc.
All the points in Crowndale's post are really relevant.  Sometimes there are unforeseen problems with a site e.g. drainage.  How do you raise the cash for that?  Perhaps also ongoing maintenance issues including grass cutting or tree surgery.  We hire a tree surgeon once a year and it's well over £100 for the day.

I really can't see £10 p.a. raising anywhere near enough to have adequate reserves (at £10 you are paying way under the average).  Our water rates alone are £5 p.a.

Consider how much it would cost to print your invoices, buy envelopes and post them out.  And that's before reminder letters, warning letters etc.  I doubt the parish would provide a post-devolvement subsidy for this - and even if they did to start with, they have limited funds and you can bet your bottom dollar that this type of funding may be a target if and when cuts need to be made.

Other things to consider include how you would resolve disagreements within the committee - whether personality clashes or differences of opinion re organic / warning letters policy / who gets kicked off etc etc.  I think you'd also have to get public liability insurance cover for the site.

Grants for allotments are not as widespread as in the past - and they usually come with a community involvement requirement, not just to benefit existing plotholders.

Some self-managed sites thrive, don't get me wrong, it's the right course of action for some sites.  But I think you are right to be concerned at what's behind the parish's suggestion.