If they are separately funded projects the platforms won't necessarily be part of the station (buildings) improvements work.
In fact I found this job divides up three ways. The station improvements are partly paid for by the National Stations Improvement programme (NSIP) and partly by the DfT 'Access for All' fund. The former deals with general improvements to station buildings, canopies, waiting rooms, ticket offices, the latter is a specific ring fenced sum and deals with stuff like new lifts, new footbridges, ramps, tactile surfaces, contrasting handrails etc, primarily to provide access for the disabled.
The platform lengthening is a separate project, and comes under the umbrella of 'Midland Main Line train lengthening', which is part of the HLOS capacity improvements to allow 10 car trains to call. It is not due to complete 'single option selection' until Dec 2010, with construction to be complete March 2012. This is according to the latest enhancement plan update published last month.
