Being within current copyright - and UK issues - a score online would be unusual.

(The Brits seem to have a slew of hungry solicitors seek out copyright infringment)

I like the UCLA - Music Library for research - their MELVL - brought this up for your UK location.

Up Pompeii - Musical Score
World Library Scores
ST PANCRAS
LONDON, NW1 2DB
United Kingdom

British Library Reference Collections

London, NW1 2DB United Kingdom

Up Pompeii"
(Main Theme)
Written by Ken Howard and Alan Blaikley
Sung by Frankie Howerd (uncredited)

ocument Type: Musical Score
All Authors / Contributors: Ken Howard; Alan Blaikley
Find more information about:
OCLC Number: 497291484
Description: 1 score.
Responsibility: Ken Howard ; Alan Blaikley.

The online "Sheet Music Warehouse" UK, has it for ll pounds.

The You Tube version is easy to work a fake I,IV,V ...from ... even the tuba is simple.

Multiple midis abound IE http://www.midisite.co.uk/midi/search.pl?t=rome&s=50&m=&x=50

Sincerely,
Gargoyle