Thanks a lot - that did the trick!
Ran a few tests for comparison and its a lot smaller.
API 1.4 - IDE 1.6.5
Sketch uses 14,324 bytes (99%) of program storage space. Maximum is 14,336 bytes.
API 1.5 IDE 1.6.5
Sketch uses 14,504 bytes (101%) of program storage space. Maximum is 14,336 bytes.
API 1.6 dev IDE 1.6.5
Sketch uses 12,240 bytes (85%) of program storage space. Maximum is 14,336 bytes.
Thanks for the tip. That serial debug really helped.
I can see the data being send and received to the ethernet gateway. Telnet to the ethernet gateway on port 5003 and I can then see some data when I press a button.
This leads me to believe its a problem my domoticz. Will keep digging.
Update: I installed mysensors controller and its working perfectly now! Node and sensor picked up. When I press the button it registers on the controller! Woo hooo! 
Thanks - been racking by brain over this. Going back to 2.0.0 also works for me.
@ripperle I gave up with them and used a nodemcu with a esp8266 wifi module. Have been running without a hitch for months now.
@emc2 Interesting read.
@korttoma I've connected up IRQ line. Still no luck,
@TON-RIJNAARD Have tried that now as well. No luck.
Tried going back to basics and now have 2 x Arduino pros with RFM69 - both loaded with pingpong script.
Don't know where I'm going wrong but I can't even start the script - entering 1 or T does nothing. (I"ve used the script before with the NRF radio and it works)
Have also tried the latest dev version.
Just keep getting this on both arduinos:
0 MCO:BGN:INIT NODE,CP=RRNNA--,VER=2.0.1-beta
4 TSM:INIT
1 MCO:BGN:INIT NODE,CP=RRNNA--,VER=2.0.1-beta
5 TSM:INIT
7 TSM:INIT:TSP OK
8 TSM:FPAR
138 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
2145 !TSM:FPAR:NO REPLY
2147 TSM:FPAR
2277 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
4284 !TSM:FPAR:NO REPLY
4286 TSM:FPAR
4416 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
6423 !TSM:FPAR:NO REPLY
6425 TSM:FPAR
6555 TSF:MSG:SEND,255-255-255-255,s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=OK:
8562 !TSM:FPAR:FAIL
8563 TSM:FAIL:CNT=1
8565 TSM:FAIL:PDT
@emc2 Thanks. Will keep digging but I"m almost out of idea as well. 
@emc2 This is all I see on the gateway:
0;255;3;0;9;Starting gateway (RRNGE-, 2.0.0)
0;255;3;0;9;TSM:INIT
0;255;3;0;9;TSM:RADIO:OK
0;255;3;0;9;TSM:GW MODE
0;255;3;0;9;TSM:READY
scandone
state: 0 -> 2 (b0)
state: 2 -> 3 (0)
state: 3 -> 5 (10)
add 0
aid 6
cnt
f r0, scandone
connected with homenet, channel 1
dhcp client start...
..............ip:192.168.1.100,mask:255.255.255.0,gw:192.168.1.1
.IP: 192.168.1.100
0;255;3;0;9;No registration required
0;255;3;0;9;Init complete, id=0, parent=0, distance=0, registration=1
pm open,type:2 0
0;255;3;0;9;TSP:SANCHK:OK
0;255;3;0;9;TSP:SANCHK:OK
@emc2 Thanks for the link.
I've connected up the missing pin and believe the wiring is all correct. Double checked the wiring on the arduino mini as well to the rfm69 (Via logic converter)
Still can't get it to communicate using DallasTemperatureSensor-RFM69.ino
Starting sensor (RRNNA-, 2.0.0)
TSM:INIT
TSM:RADIO:OK
TSP:ASSIGNID:OK (ID=5)
TSM:FPAR
TSP:MSG:SEND 5-5-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=bc:
TSM:FPAR
TSP:MSG:SEND 5-5-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=bc:
TSM:FPAR
TSP:MSG:SEND 5-5-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=bc:
TSM:FPAR
TSP:MSG:SEND 5-5-255-255 s=255,c=3,t=7,pt=0,l=0,sg=0,ft=0,st=bc:
!TSM:FPAR:FAIL
!TSM:FAILURE
TSM:PDT
@korttoma That probably explains why I can't get it working. Do you know what pin it needs to connect to on the nodemcu?
On this link the DI00 is gray (https://www.mysensors.org/build/connect_radio) but here it doesnt show where to connect it (https://www.mysensors.org/build/esp8266_gateway)
Thanks - I can only think my connections are wrong then. Can't get any comms going on the rfm69.
@FotoFieber Did you come right with the RFM69? I also struggling to get it working and need to confirm the wiring diagram.
After many months of struggling with the poor range of NRF24L01+ (And having tried all the tricks) I'm not trying my luck with the RFM69 radio. (RFM69CW - 868Mhz)
When connecting the rfm69 to the nodemcu (For the ESP8266 gateway), is a 5v to 3.3v logic level converted required?
For the projects listed it says you need one when connecting it to the Arduino but wasn't sure about the Nodemcu.
Also can someone confirm the wiring - its not 100% clear.
Is this correct?
Nodemcu ---> RFM69
D2 ---> N/C
D8 ---> NSS
D5 ---> SCK
D7 ---> MOSI
D6 ---> MISO
N/C ---> D100
And of course GND and VCC (3.3v)