Hi Jessie123,
It all depends on your circumstances really - If you think that at some point you'll be moving back to the UK it may be better to leave it where it is.
As it's a Civil Service/Government Final Salary scheme then i'm pretty sure it'll be inflation proofed and subject to "Revaluation in Deferment" (ie specific annual growth rates that are outlined in the scheme booklet) and ""Increases in Payment" (once you retire it will continue to keep pace with inflation). As you have 23 years service, it's likely that you'll get a relatively good income in your retirement (as opposed to through a normal "Money Purchase" pension scheme, ie a personal pension).
However, if you intend to settle permanently in Australia, it may be worth looking at transferring the funds over to a QROPS Compliant Super (Qualified Recognised Overseas Pension Scheme), as the tax situation is generally less restrictive than UK rules.
One way to get an idea of what it's worth in "cash terms" is to ask the scheme for a "Cash Equivalent Transfer Value" (CETV) as this should give you both the expected annual income at your retirement date and also the actual monetary value on transfer. That's a basic outline, but there's obviously a lot more in depth rules and regulations depending on the value of the fund etc.
I've worked in Financial Services in the UK before emigrating and now I work in Australian FS, so if you need any help or info give me a shout and i'll see what I can do :-)