First, charities where there is no .co.uk equivalent, or where they own them as well, can take up the .uk equivalent from 10 June. For the majority (53%) of those with .org.uk registrations, including many of the largest charities in the UK, this will be an option. In the meantime, .org.uk registration carries on as normal. There is no need to wait for any period of time to progress your domain name strategy.
Secondly, there is an implicit assumption that a .co.uk winning the equivalent .uk domain is inherently abusive. In fact, there are many legitimate uses of a domain name - including long established businesses and charities that hold the same strings.
Thirdly, any charity - or indeed any registrant - who feels that another registration is infringing their rights - can have their complaint examined at any time by our well respected Dispute Resolution Service. Anyone that has established usage rights to a term or phrase or character strings has had, since 2001, an independent, effective and low-cost means of contesting registrations which take unfair advantage of their rights. This can deliver a ruling within as few as two months, although many cases are quickly settled amicably through a mediated process. Thankfully the number of cases is very low in the context of over 10m .uk domain registrations, but I would encourage any charities who feel that their brand is being infringed to make use of that process.