I work in Sutton
I'm only level 25 though and my monsters are shite
As long as the group has enough people it doesn't matter - up to 20 people so if you had that many I reckon everyone could be level 25 or less. Shite monsters are ok as long as you can choose the ones with the right type attacks:
Lugia is Psychic and Flying so pokemon with Rock, Ice, electric, dark or ghost -eg: Gengar, Tyranitar, Golem, jolteon
Articuno is ice and flying so pokemon with Rock, electric or fire - especially rock as that's super efefctive against both ice and flying so double damage. eg: Golem, jolteon, tyranitar, flareon, charizard, arcanine.
Don't let pogo autoselect chansey, blissey, snorlax or fucking wobuffet as none of them do much damage attacking. Snorlax might be ok but you've probably got better.
Remember that you can rejoin a raid after your first team have fainted so it doesn't matter if you get all knocked out, just jump back in - you lose bonus balls for the damage you did with the first team but it can make the difference between winning or losing the raid, so it's better than putting in a Blissey at the end to make sure you last till the end of the fight.
If you want an invite to the discord which has a channel for sutton raids, let me know (just to check, I'm talking about Sutton Coldfield near Birmingham, not Sutton London).