A decade ago or so one would have reasonably expected to see some sort of RAF AT aircraft flying in aid. Given the Op tempo over the past 10 years there are unlikely to be any spare assets available.
On a slightly more positive note a British Airways 747 left the UK (via Denmark) today carrying relief supplies bound for Haiti. The entire cost of the aircraft (incl fuel) is being borne by BA.
Security concerns hampers Haiti aid effort - Times Online
Regards