http://www.planetx.co.uk/i/q/TYSCMRCFOL/schwalbe-marathon-cross-wired-tyre-with-raceguard
Had a pair of these on my FatNotFat wheels since late summer last year, they roll very well, cost me £20 from NextDayTyres and they normally cost ~£23 now… £16 is a steal!
Fitting by hand, no levers, took me less than 1 minute per tyre. Even I was shocked, after my fun with 25c Marathon Plus on my Felt years ago!
There’s a bit of debate on the actual spec, but PX also have some G-Ones for ~£20 IIRC. Doesn’t seem to be the new model G-One speed, but the older model was supposed to roll well, albeit there is question mark over their durability.
Another new addition to stock at PX is the Panaracer Gravel King SK for ~£25 each, a little googling earlier suggests these might be a strong competitor to the G-One Speeds