hi tom,
i don't know about engineering, but the ESRC wrote in this years guidelines to PhD funding applications, that they are at the moment in the process of reconsidering their policy of paying P/T students merely "fees only" stipends. They approve of P/T studying and are thinking of funding P/T students fully in the future, perhaps already starting this autumn. perhaps something similar is going on in the other research councils. it would be worth contacting them directly to find out.