are all these updates taking up space on my Touch, is that what 'Other' is as shown on the bar on the Summary page ?
Yes - partially.
Each update overwrites the previous one. The updates are saved and installed on a separate partition to your media, therefore, you are not losing any space installing official updates from Apple.
Incorrect - because I just tested this. On 1.1.2 firmware (pre-5 extra apps), max formatted capacity 14.84GB, "Other" 18.4MB. On 1.1.4 firmware, max capacity still 14.84GB, "Other" now 103MB.
That jump represents the new, non-standard (1.1.3) applications [edit - which install whether or not you pay to unlock them]. The OS itself, the default apps, and related data apparently are stored in a separate 300MB partition - that's not part of your 14.84GB. OS updates write to this, so they don't impact your max space.
Everything else - for now, the 5 January apps. -
does impact your max space. Expect any future stand-alone apps, any firmware updates that include apps, or any firmware updates where you have to pay to unlock the apps

to similarly chip away at your max space.
[Editorial]Apple is dumb to bundle these together, as you can see the snowball effect multiple firmware + locked app updates would have. It's like having a forced, locked copy of iWork stuffed into each Security or OS X update. Why they can't just push them separately... [/Editorial]