Well after numerous failed attempts to download the recovery image I finally got it. The zip tests ok but it would be good to verify its hash. The hashes on mine are as follows
Name: SurfacePro4_BMR_155_2.114.0.zip
Size: 5.34 GB (5,742,435,022 bytes)
SHA1: EDDB15782ADD069934A4E764DBB2FDB1C0EC4F4E
SHA256: 37E4086822278DE8C3B5C79107D50CA9042C28DC472A7588473FC1A0F83AD03C