I've worked it out. The value stored in sysindexes.first, sysindexes.root and sysindexes.firstiam can be turned into a file id and page number by splitting the value in two and then reversing it...

For example we have the following value 0xA16F03000100 in sysindexes.first.

Split this into two parts A16F03 (the page id) and 000100 (the file id).

To find the page id:

Reverse the first half - 036FA1 (the page id).

Then convert this to decimal (google: convert 0x036FA1 to decimal) - 225185 (the page id).

Now if you were to use DBCC PAGE command with the page 225185 you'll see your data.

Joe