Senior Railcards are £26 but require either an existing railcard, driving license, passport or birth certificate as proof of age (60+), a bus pass is not officially proof of age for the railcard. Generally speaking there is a 34% discount on most rail fares with a Senior Railcard.

National bus passes can be used on rail lines local to the issueing council/PTE with varying benefits.

As for the spotting, 90s can be seen on the GEML between Norwich and London Liverpool Street, on Freightliner services around the country and there is a 'Pretendelino' and Scotrail Sleeper services out of Euston.

86s are freight only these days, and mostly on Freightliner trains, but 86101, 86701 and 86702 can be found out and about on mail trains and have recently been used on test trains into Stansted. 86901 and 86902 (Network Rail yellow) were somewhere on the WCML last Friday (17th), at Crewe I think (it was there or Warrington Arpley). 86101 was with 87002, 67029 and 67005 (and some 325 EMUs) at Warrington RMT (north of Warrington Bank Quay) on that day too.

67s are in regular use with Wrexham and Shropshire between Wrexham and London Marylebone and operate as 'Thunderbird' rescue locos on the ECML. There is a fair chance you might see one at Warrington also.

73s will be tricky to see, there aren't many about. Network rail use them on test trains mostly around the southern region,and GBRf have some in use too, Peterborough might have a couple on site.

where to see classes 67 &73 alternate locations
 

Toton has an allocation of 67's (in EWS RED/gold) though only a few remain on shed at any one time
and as for 73's then a good place to see quite a number of these is Barrow Hill as they go through service here not sure if it's Nemesis or Harry Needle who does it

When you already have a SSRC you only need produce the old card to get a new one.