You should first try the International Genealogical Index (IGI) at- www.familysearch.org
for your grandfather. There is a likely candidate under the IGI heading (ignore the various Census returns) and it looks as though someone is already researching this line because of the inclusion of the Death Date etc.
To find out about siblings, reset the search page and then key in the father's First and Last Names in the appropriate fields at the top-right, followed by the mother's first name ONLY in that appropriate field.
This may bring up a list of responses, which you will have to read through to sort out the likely siblings.
After that, you should go to-
www.pro.gov.uk (Credit Card charge)
to get more detail and if required, copies of the appropriate records.
Be wary, you should check out each step carefully and not assume that just because "the name is the same", that you have definitely found the correct person/s.
You may also find the following sites useful-
Modern maps- www.multimap.com (and Aerial Photos) www.streetmap.co.uk