hmm.. Tesco's range of fizzy booze is pretty good.
Cava wise i rather like...tescos finest, marques de monistrol, cordorniu, freixenet (in that order, freixenet seems less memorably good). Usually i prefer the pink versions of the same thing.
Sect is good if you can get it (Asda used to do it at £3 per bottle, bloody great..haven't seen it for a while though)
Prosecco - seems new to the market - didn't really notice it before this year... There was one with a bright yellow label i Sainsbo's that i rather like..ah this one but i ws in London central so paid more for it.
non-champage 'others' - veuve de vernay - Tescos - very good. Blanc de Blanc - great. really great. Blanc de Noir (Tecos) - also good. Blanc de Noir (sainsbos) - you used to get in magnum sized bottles - i loved that stuff.
i usually avoid sparkling chardonnay eg Jacobs Creek, Hardys but is still drinkable.
actually my choice is generally guided by 'what is on offer and in stock given my budget'
i think next time i go bottle-hunting the Prosecco might get first call, if only because it still has novelty value.
the only one i've had that seemed really over-sold was M&S Oudinot. Pile of crap for the price.