Is a Design and Access Statement required as part of the application documents

Such a document is not specifically listed in the Infrastructure Planning (Applications: Prescribed Forms and Procedure) Regulations 2009 (the APFP Regulations). It is noted however that APFP Regulation 5(2)(k) notes, where applicable, a plan identifying any new or altered means of access must be submitted. APFP Regulation 5(2)(o) notes the submission of any other plans, drawings and sections necessary to describe the proposals for which development is sought, showing details of design, external appearance ... means of vehicular and pedestrian access, etc.
If the proposal is EIA development, then the Environmental Statement will need to, as a minimum, include "a description of the development comprising information on the site, design and size of the development" (Infrastructure Planning (EIA) Regulations 2009, Regulation 2(1) and Schedule 4, Part 2).
You may also be aware of Section 4.5 of National Policy Statement EN-1 which provides guidance on "Criteria for "good design" for energy infrastructure". The NPPF acknowledges that 'good design is a key aspect of sustainable development' and Design Council CABE have published Design Guidance in 2012 on NSIPs.
Whilst there is no express requirement for a separate Design and Access Statement, you will need to satisfy yourself that within the application documents submitted there is sufficient information to satisfy the requirements in APFP and EIA Regulations and due regard has been had to other relevant matters.