Does this look like your Isabella Pendergast ??

Birth Reg
Isabella Pendergast
Registration Year: 1887
Registration Quarter: Jul-Aug-Sep
Registration district: Salford
Inferred County: Lancashire
Volume: 8d
Page: 87

1891 Census
Name: Isabella Pendergast
Age: 4
Estimated birth year: abt 1887
Relation: Daughter
Father's name: Frank Pendergast
Mother's name: Alice Pendergast
Gender: Female
Where born: Manchester
Civil Parish: Birmingham
Ecclesiastical parish: St Luke
Town: Birmingham
County/Island: Warwickshire
Country: England

Frank Pendergast 35
Alice Pendergast 29
Frank Pendergast 11
Lawrence Pendergast 9
M Alice Pendergast 7
Isabella Pendergast 4
Alfred Pendergast 1


1901 Census
Name: Isabella Pendergast
Age: 14
Estimated birth year: abt 1887
Relation to Head: Daughter
Gender: Female
Father: Frank Pendergast
Mother: Alice Pendergast
Birth Place: Salford, Lancashire, England
Civil Parish: North Manchester
Ecclesiastical parish: Harpurhey Christchurch
County/Island: Lancashire
Country: England

Frank Pendergast 40
Alice Pendergast 35
Mary Alice Pendergast 17
Isabella Pendergast 14
Alfred Pendergast 12
Ada Pendergast 7
Sidney Pendergast 4
Frederick Pendergast 2

Queensland State Archives; Registers of Immigrant Ships' Arrivals
Name: Isabel Pendergast
Age: 22
Birth Year: abt 1888
Place of Origin: Lancashire, England
Ship Name: Perthshire
Port of Arrival: Brisbane
Arrival Date: 26 Dec 1910

It certainly does!
Thanks very much for your help.
Also for the immigration info that was previously unknown.

1881 cvensus
Name: Frank Pendergast
Age: 29
Estimated birth year: abt 1852
Relationship to Head: Head
Spouse: Alice Pendergast
Gender: Male
Where born: Manchester, Lancashire, England
Civil Parish: Bury
County/Island: Lancashire
Country: England
Street address: 2 Bk Parsons Lane
Marital Status: Married
Occupation: Telegraph Linesman Railway
Registration district: Bury
Sub registration district: North Bury
ED, institution, or vessel: 1

Frank Pendergast 29
Alice Pendergast 19
Jno. Francis Pendergast 3 months born: Bury, Lancashire
........................................................................................

From the list below it would appear that this family moved around poss to do with Frank's occupation - Telegraph Linesman Railway.

Not sure when Alice or Frank were born, thier ages seem to suggest different years on each census. [1881 19-29, 1891 29-35, 1901 35-46, 1911 47- 56.]

Frank Pendergast Born Manchester Lancashire
Alice Pendergast Born Cardiff Wales
Jno. Francis Pendergast born: Bury, Lancashire (shown as Frank on 1891 census)
Lawrence Pendergast born Bury, Lancashire
Mary Alice Pendergast born: Newport, Monmouthshire, Wales
Isabella Pendergast born: Manchester / Salford, Lancashire
Alfred Pendergast born: Birmingham Warwickshire
Ada Pendergast born Birmingham, Warwickshire
Sidney Pendergast born Birmingham, Warwickshire
Frederick Pendergast born Birmingham, Warwickshire
Lilly Pendergast born Harperhey, North Manchester Lancashire

.......................................................................................

1911 census
Name: Frank Pendergast
Age in 1911: 56
Estimated birth year: abt 1855
Relation to Head: Head
Gender: Male
Birth Place: Greater Manchester, England
Civil Parish: South Manchester
County/Island: Lancashire
Country: England
Street address: 13 Victoria St Rusholme M/C
Marital Status: Married
Occupation: Electrician Out Of Work
Registration district: Chorlton
Registration District Number: 464
Sub-registration district: Ardwick
ED, institution, or vessel: 63
Piece: 23764

Frank Pendergast 56 Occupation: Electrician Out Of Work
Alice Pendergast 47
Alice Pendergast 26
Ada Pendergast 18
Lidney Pendergast 14
Fred Pendergast 11
Lilly Pendergast 9
Frank Pendergast 30 (Jno. Francis - lists occ as man of leisure ?? )

.......................................................................................

Marriage
Name: Frank Pendergast
Registration Year: 1879
Registration Quarter: Jan-Feb-Mar
Registration district: Salford
Inferred County: Lancashire
Volume: 8d
Page: 144
Spouse : Alice Burnett

This looks like Frank and Alice's marriage and if it is, Alice would have been 17 years old according to the 1881 census

If you want to go further back with each of Isabella's parents and in view of the age differences list in the census I would suggest you get the marriage cert using the data above.

Could be Alice's birth reg:

England and Wales, Birth Registration Index
Name: Alice Burnett
Event Type: Birth Registration
Registration Quarter: Oct-Nov-Dec
Registration Year: 1861
Registration District: Cardiff
County: Glamorganshire
Event Place: Cardiff, Glamorganshire, Wales
Volume: 11A
Page: 216
Line Number: 134

That's fantastic! Thanks so much.
Your information certainly gives me something to work with.
I'd like to go back a fit further, so will see what I can come up with.

You can order Frank and Alice's Marriage cert via the link below its around £9 plus P&P

www.gro.gov.uk/gro/content/certificates/

Thank you.