I used some M6 (I think) Connector Nuts from Toolstation as the spacers, just used some longer bolts and added the nuts between the cradle and the heater (a bit fiddly to get the nuts in just the right place when tightening them up)
I used a 90-60mm at one end
https://www.ebay.co.uk/itm/223621209175 and a 90-63mm on the other
https://www.ebay.co.uk/itm/351610333816 cutting them shorter to suit.
The cradle I bought complete off eBay so I don't have the details for all the parts.