Hi. Can anybody help? I have an Worcester Greenstar Heatslave boiler (2008) with an internal digital programmer which is playing up. The programmer has 3 programmable periods for both CH and HW but when I have tried to find a replacement with the part no (7716192033) there only seem to be units with 2 periods. They all look the same as the original unit but I ideally want 3 periods. Is it possible to fit a Worcester Comfort programmer instead? Did the programmer change to just 2 periods? It seems strange that if it did it retained the same part no. Many thanks.