Mat Bowles

there is a right-wing consensus in mainstream politics

Disagree that it's "right wing". It's further to the right of either of us, but it's centrist rather than right—the current consensus is centrist, corporatist and vaguely authoritarian.

wouldn't fit with the positioning as a 'centrist' party

I don't see the positioning as 'centrist'—the positioning is Liberal, which is neither left nor right on the 20C scale but opposed to the current corporatist consensus (which is why Cameron's posturing works as all he has to be is more liberal than the Govt, he doesn't have to be a liberal as us).

What would be the point of this? Individual voters can already give £3

It's a direct lift from the Power Commission report—I've got the full report in a book, they were giving htem away free, but it's on site, the Exec Summary is worth a read, from which:

20.  State  funding  to  support  local  activity  by  political  parties  to  be  introduced  based  on  the 
allocation of individual voter vouchers. This would mean that at a general election a voter will be 
able  to  tick  a  box  allocating  a £3  donation  per  year  from  public  funds  to  a party of  his or  her 
choice  to  be  used  by  that  party  for  local  activity.  It  would  be  open  to  the  voter  to make  the 
donation to a party other than the one they have just voted for.

Not sure I'm sold on it completely, but note it's public funds (ie taxation) not donations, but under control of voters, and it can help smaller parties build up a local base, etc. It's a much better idea than the state funding solution proposed by the Big Two anyway.

Poor areas can't afford as much as rich areas, so this would perpetuate and increase inequality.

Bulk of, not all of—he's very much aware of the problems in the US where this is the case. Note it's "the bulk of" not "all of"—it used to be that LAs took all business rates take, now it's centrally allocated, for example. Personally I'd bring in LVT and then have central grants for redistributive purposes, it's daft to raise most of an LAs budget nationally.