UTF-8 and =, LIKE problems

I am running a web-based accounting package (SQL-Ledger) that supports
multiple languages on PostgreSQL. When a database encoding is set to
Unicode, multilingual operation is possible.

However, when a user's input language is set to say English, and the
user enters data such as "79", the data that is sent back to PostgreSQL
for storage is U+FF17 U+FF19, which are the Unicode half width
characters "79". So far so good.

Now, if the user switches languages and enters "79" as a search key, the
previously entered row will not be found with the LIKE or = operators,
and all other comparison operations will fail too. The problem is that
the browser now sends back U+0037 U+0039, which are Unicode full width
characters for "79".

Semantically, one might expect U+FF17 U+FF19 to be identical to U+0037
U+0039, but of course they aren't if a simple-minded byte-by-byte or
character-by-character comparison is done.

In the ideal case, one would probably want to convert all full width
chars to their half width equivalents because the numbers look wierd on
the screen (e.g., "7 9 B r i s b a n e S t r e e t" instead of "79
Brisbane Street". Is there any way to get PostgreSQL to do so?

Failing this, is there any way to get PostgreSQL to be a bit smarter in
doing comparisons? I think I'm SOL, but I thought I'd ask anyway.

...Edmund.