I have two-and-a-half Heljan Hymeks, half a Western, and one of their 1366 class pannier tanks. All bought at substantial discounts, and all for conversion to P4.
When Howes of Oxford were running the Heljan spare parts service years ago, I frequently hoovered up whatever they had available, including a set of spares for the Met Bo-Bo, as they were useful for detailing a resin Bo-Bo body. Likewise, the Hymek bogie casing is the correct overall wheelbase for a CIE Sulzer.