I thought I'd probably have to do something manually to sort this out, and sure enough I did...

 The summertime to wintertime changeover occured this morning.

To sort out the time, you have two steps.

Setup 464981/10 {
  Version        = 6981
  CableType      = 3
  BannerTimeout  = 0
  SetupDate      = 11698
   Source         = 464981/1394
  CallWaitingPrefix = {}
  DialPrefix     = {}
  ScartSettings  = 464981/12
  ServiceInfo    = 464981/11
  RFOutputChannel = 21
  LastChannel    = 464981/292
  PostalCode     = DE74
  VCRIrCodeNum   = 0
  NoPrivateBackhaul = 0
  Complete       = 7
  DemoMode       = 0
  LastCallStatus = Succeeded
  LastCallAttempt = 1256290464
  LastSuccessCall = 1256290464
  NextCallAttempt = 1256860800
  ServiceState   = 5
  ServiceStateExpiration = 14547
  TimeZone       = 9
  IndexPath      = /Setup
} 

The two bits in bold are the bits you need, so at the TiVo prompt I needed to do the following

 ./dbset 464981/10 TimeZone 8

This takes your timezone back one hour. 

Next, you need to change the time forward one hour. Yes, it's bizarre, but otherwise it won't work!

So I first found out the date, then changed the time accordingly

bash-2.02# date
Sun Oct 25 03:52:54 localtime 2009
bash-2.02# settime 20091025045355
Time set to: Sun Oct 25 04:53:55 2009
Have a nice day.
bash-2.02# settime -rtc
Time set to: Sun Oct 25 04:54:04 2009
Have a nice day.

Job done! 

Come summertime, the reverse is needed.