If you are not granted legal aid it is possible to obtain free legal advice from the Community Legal Services [
http://www.communitylegaladvice.org.uk ] phone line. Alternatively there might be a law clinic near you.
If you are prepared to spend time doing some research and filling in forms it is also possible to represent yourself. With children cases there isn't usually that much law involved. The application form, C100, and guides CB1 & CB3 can be downloaded from;
http://www.hmcourts-service.gov.uk/HMCSCourtFinder/FormFinder.do
There is a fee of £175 and if you are on a low income you will be exempt (Form 160).
However, in England & Wales, grandparents need to seek permission from the court before going ahead with the application. Court officials could help you with this and check any forms have been filled in correctly, but they cannot say anything which might be construed as legal advice.