Yes, Hamstall would suggest Staffordshire - Hamstall Ridware.
This may very well be clutching at straws BUT

As we have been given death dates for Percival and Sarah, I looked at FreeBMD to find a Percival with any surname who died in June quarter 1902 - a lot of them were aged 0, so could be discounted. However, there is a death registration for Percival TUNSTALL in that quarter in Poplar. SO I looked at the 1901 Census for Percival Tunstall - there he is, born Stafford, a Joiner, and aged 67, in Stepney Workhouse with wife SARAH aged 77, born Manchester. There is a death registration for Sarah Tunstall in Poplar District in December quarter 1901. I haven't dared to look for a marriage.
Or is that too much of a coincidence?

Or more likely - have I lost the second braincell again?