I am not in a position where I can spend huge amounts of time down in London. However if this only requies a minimal amount of "on-site" time then I might consider it.
Oracle and TikiWiki could be a big problem. There are many outstanding problems in that transition, and the oracle support is quite small.
Ratings are coming in 1.9/1.10 releases mainly from mose. and secure search results are 1.9 already, but only supported by MySQL as other databases do not have the required functions to filter the results based on the current way the data is stored in the TikiWiki database.
Anyway, for consultancy and development, all my pricing is at http://shop.damosoft.net.