I've solved it! for anyone elses info it was simply a combination of daft mistakes (see below).

I had not taken into account duplicate column names in the generated view (so I added aliases), a "time saving" copy and paste idea had resulted in the use of some incorrect table names, also I had not added AND operators when defining the joins in the WHERE clause. So the corrected statement is as follows:

CREATE VIEW LLPG AS
SELECT PR_BLPU.KEYVAL BLPU_KV, PR_BLPU.UPRN, PR_BLPU.MAP_EAST,
pr_BLPU.MAP_NORTH, PR_BLPU.LOGICAL_STATUS BLPU_STATUS,
PR_LPI.KEYVAL LPI_KV, PR_LPI.PKEYVAL LPI_PKV, PR_LPI.ST_KEYVAL LPI_SKV,
PR_LPI.ADDRESS, PR_LPI.CURRENCY_FLAG, PR_LPI.LOGICAL_STATUS LPI_STATUS,
PR_LPI.PAO_START_NO, PR_LPI.PAO_START_SFX, PR_LPI.PAO_END_NO,
PR_LPI.PAO_END_SFX, PR_LPI.PAO_DESC, PR_LPI.SAO_START_NO,
PR_LPI.SAO_START_SFX, PR_LPI.SAO_END_NO, PR_LPI.SAO_END_SFX,
PR_LPI.SAO_DESC, PR_LPI.POSTCODE, PR_LPI.POST_TOWN,
PR_LPI.OFFICIAL_ADDR,
PR_ST_DESC.KEYVAL DESC_KV, PR_ST_DESC.PKEYVAL DESC_PKV, PR_ST_DESC.STREET_NAME,
PR_ST_DESC.LOCALITY_NAME, PR_ST_DESC.TOWN_NAME,
PR_ST_DESC.COUNTY_NAME, PR_ST_DESC.TRADING_ESTATE,
PR_ST_DESC.DISTRICT_NAME, PR_ST_DESC.POSTAL_TOWN,
PR_ST_DESC.POSTAL_COUNTY,
PR_STREET.KEYVAL STREET_KV, PR_STREET.USRN
FROM PR_BLPU, PR_LPI, PR_ST_DESC, PR_STREET
WHERE
PR_BLPU.KEYVAL = PR_LPI.PKEYVAL
AND
PR_LPI.ST_KEYVAL = PR_ST_DESC.KEYVAL
AND
PR_ST_DESC.PKEYVAL = PR_STREET.KEYVAL;


I found a trial version of TOAD ( a simple SQL GUI application) really helpful in working out what was wrong.