Sorry to disappoint, but I don't believe this to be Powell or Whitefriars. There are too many factors that suggest other manufacturers could have made it. Other than the general style there is little that suggests Powell.
Don't forget that this type of item is synonymous with a period rather than one company. Furthermore that period relies on historic pieces for its inspiration.
Factors like the milled trail and the raspberry prunts were used by various manufacturers and in a number of countries between around 1880 and the beginning of the First World War. In my opinion the ones on this vase are not consistent with Powell.
Unfortunately, there are also a number of manufacturers on the Continent who have reproduced pieces like this in recent years.
You don't tell us about the pontil, although I don't feel it critical to my opinion it may help point to the right direction. Is it broken or polished? If polished in what way? Regular/irregular, central, etc.?