We have a Twyford toilet cystern which we think needs changing. My husband bought a new syphon for it, but when he removed the cystern we have found it has two large cracks running across the porcelain outside. You can't see the cracks on the inside of the cystern, but they look ominous and we think it may be safer to change the whole cystern. The only info printed into the cystern is S7 and Jan 1978. It doesn't even say it's Twyfords, but that's what is on the toilet pan, so we assume it is a Twyfords cystern. I am uploading a photo of the bottom/fittings of the cystern and would be very grateful for any info on how to purchase a cystern to fit the existing toilet. Many thanks