OK, so while I was quite willing to pay over money for the HS3 GC plugin, it didin't provide what I wanted - a way to send IR from a script.
(ALL Event) Scripts use a simple way of setting devices values using strings (see whinge later) -
_Device("Family Room Lights") = "On"
(Get the value using x = _Device("Family Room Lights")
Note they are strings - no technology specific 'magic numbers' here!

I wrote a plugin (HSPI_ScriptDevice) which calls a script for a device.
This insulates the operation to the device from the underlying technology,
even abstract/status devices like House Occupancy!
So I dim a light using 0-100%, not 0-32 for LightwaveRF etc. it abstracts the technology from the operation.
ALL my devices with the exception of Z-Wave (darn it!) are 'ScriptDevices'
Now I couldn't find callable GlobalCache function(s) in the HS plugin.
Also once the code is in HS I can't tweak it (to change the repeat).
Final 'nail in the coffin'? I don't think it shows up on the device management/status pages.

So I wrote my own, simple (IR blaster only) ScriptDevice.
(GlobalCache provide a VERY useful ,easily found, API - except for [6] below!)

Here it is (numbers in '[]' are for reference) -
Imports System.Net.Sockets
Imports System.Threading
Imports Scheduler.Classes

'Module _GlobalCache
Private Const myScript As String = "_GlobalCache.vb"
Private Const IRTimeout As Integer = 200
[0] Public Function IR(ByRef Parms() As Object) As String
Dim r As String = ""
Dim d As Integer = CType(Parms(0), Integer)
Dim n As String = CType(Parms(2), String)
Dim q As DeviceClass = CType(hs.GetDeviceByRef(d), DeviceClass)
'Dim q As Object = hs.GetDeviceByRef(d)
[1] Dim a As String = q.Address(hs) 'Config file
[2] Dim s As String = q.Location2(hs) & " " & q.Location(hs) & " " & q.Name(hs)
s = s.Replace(" ", " ")
s = s.Trim()
hs.WriteLog(myScript, s & " press " & n)
Dim k() As String = n.Split(","c)
For i As Integer = 0 To UBound(k)
k(i) = hs.GetINISetting(s, k(i), "", a)
hs.WriteLog("", "For " & k(i))
Next i
'read IP and IR from INI or default
[3] Dim ip As String = hs.GetINISetting("General", "IP", "", a)
Dim st As New SenderIR(ip, k)
Dim t As Thread = New Thread(AddressOf st.SendIR)
If (t.Join(IRTimeout * UBound(k))) Then r = st.myResult Else r = "IR Error!)"
Catch ex As Exception
hs.WriteLog(myScript, "" & ex.ToString)
r = "IR Exception!"
End Try
'never return what was supplied, or couldn't repeat it
[4] Return r
End Function
#Region "Private IR class"
[5] Private Class SenderIR
Private Const IRPort As Integer = 4998
Private myIP As String
Private myIRs() As String
Public myResult As String
Public Sub New(ByRef IP As String, ByRef IRs() As String)
myIP = IP
myIRs = IRs
myResult = ""
End Sub
'public (thread) method
Public Sub SendIR()
Dim c As TcpClient = Nothing
Dim s As NetworkStream = Nothing
Dim w As System.IO.StreamWriter = Nothing
Dim r As System.IO.StreamReader = Nothing
Dim t As String = ""
c = New TcpClient(myIP, IRPort)
s = c.GetStream()
w = New System.IO.StreamWriter(s)
r = New System.IO.StreamReader(s)
For i As Integer = 0 To UBound(myIRs)
If (myIRs(I) <> "") Then
w.WriteLine(myIRs(i) & vbCr)
[6] 'fibs, doesn't send back a line with a CR on the end!
Dim b(64) As Char
Dim rx As Integer = r.Read(b, 0, 64)
t = New String(b)
If (t.Contains("ERR")) Then myResult = "IR Fail!"
End If
Next i
Catch ex As Exception
'hs.WriteLog(" ", "Send " & ex.ToString())
myResult = "IR Exceptioon"
End Try
If (Not (r Is Nothing)) Then r.Close()
If (Not (w Is Nothing)) Then w.Close()
If (Not (s Is Nothing)) Then s.Close()
If (Not (c Is Nothing)) Then c.Close()
End Sub
End Class
#End Region
'End Module

IR [0] is the function called by the HSPI_ScriptDevice, standard HS parameters.
Internal class [5] sends to the GC (and can be ignored).
it uses a simple Ini file, [1] passed to the device by HS/HSPI_ScriptDevice.
As you can see, my GC is at [3], but it will find the -
line in the Ini.

Device section in the Ini, full name [2], looks like -
[Ground Family Room Plasma]
Easy to edit/change
the 4444 is just a ref number, anything is fine if not overlapping requests
the :3 is the blaster
the number after the 34500 is the repeat - plasma wants a repeated ON
Can put buttons onto the device managment screen which also show on the device status screen.
(Status reporting is a bit redundant as even if the GC received and sent the IR who is to say the cat isn't sitting in front of the blaster?)

If you're NOT using my HSPI_ScriptDevice (and who is?) then it isn't directly usable.
But as you can see, send the class [5] the 'sendir...' strings and off it goes.
The device is set up as an 'AnyString' [4] - so the value can be sent repeatedly if you wish.
(Aside whinge - HS seems not to like calling the plugin HSEvent if the value is set to the same value - why not!)

Thoughts, bouquets or brickbats - PM or better [rarely log on nowadays, too much to do] email me HomeSeerRemote 'at' athame.net.
(That's A simple Android VR app I wrote to drive HomeSeer, it's on the Play store.)