You can use your Interrail pass on the Elizabeth line, but not in the metro. 

In London:

Elizabeth line, Thameslink and London Overground are valid, as well as all other mainline rail operators except Heathrow Express.

London Underground, Docklands Light Railway, Trams and Buses are not valid.

NOte:as this baffles many a non-used to it European: you pay in general all TfL+Transp For London means by your cr.cd/bankcard-no need for special tickets-which in act are often not even available anymore. ONly in the night after all fares are calculated and totalled-depending om how much you use them, a MAX cap as ´day ticket´ may apply-this will also depend on times.

BUS fare at the mo is 1,65, incl. 1 transfer whithin 60 mins after 1st check. UNderground=metro go by zones and prices also vary with peak/off peak.