Hi Mary I finally made it back to the Family Records Centre and hopefully have some useful information for you, although I don't think our Fredericks are the same. I searched the indexes for 1864-66 and only came up with one Frederick Drewett:
Frederick John Drewett Quarter: Sept 1865 District: Eton Vol: 3a Page: 391
You will need all these references if you want to order a copy of his birth certificate from the General Register Office in Stockport. Details of how to do this should be on there web site. Let me know if you have any problems.
I have also searched the 1881 census for Frederick and Anne Heathcock. The most likely Drewett entry is for a Frederick Drewett, aged 17, unmarried, living at 1 Park Road, Kingston On Thames, Surrey with the Bartter family where he is employed as an assistant (presumably to Mr Bartter who is a butcher).His place of birth is given as Taplow in Berkshire and this not far from Eton so is probably in the same registration district.If you let me know Frederick's parents names when you get the birth certificate I will happily look and see if I can locate them too. I could not find a Charlotte Drewett who looked the right age and came from the same part of the country but she could have been born elsewhere or already be married.
The following entry is the most likely for Anne Heathcock:
Dwelling: High Street Census Place: Kingswinford, Stafford, England Source:FHL Film 1341694PRO Ref RG11Piece 2896Folio 64Page 17
David Heathcock Married 31 Born; Lye, Worcester, England Rel: Head Occ: Commercial Clerk (Chain) Sarah Heathcock Married 33 Born: Delph, Stafford, England Rel: Wife Annie M Heathcock 5 Born: Quarry Bank, Stafford Rel: Daughter Occ: Scholar Edith Heathcock 4 Born: Quarry Bank, Stafford Rel: Daughter Occ: Scholar Frederick Heathcock 1 Born: Quarry Bank, Stafford Rel: Son Mary A Heathcock 13 Born: Lye, Worcester Rel: Niece Occ: Nurse Domestic Servant
I hope all this is of use to you. Let me know how you get on.