Thank you Breadbasket. I could not find 135 either. I was assuming (maybe wrongly) that if it was a town other than Belfast, it would have included that in the address on the certificate.
The marriage, in the Mariner's Church, details are as follows
12 April 1873
Groom: William Sillery full age bachelor flax dresser 41 Everton Street groom's father: William Sillery labourer
Bride: Matilda Wilson full age spinster mill worker 135 Cambridge Street bride's father: James Wilson mariner
Thanking you,