OP, I can offer my personal experience, from my going to furry (and other) cons for close to twenty years. Mine is that furcons are generally fun for everyone except, perhaps, very shy, introverted people (and I think the notion that much of the fandom is of that type seems to be wrong). You can absolutely have lots of fun without porn or drugs.
>Want to get laid
They're not meet markets. You can get laid, but most people aren't focused on that alone.
>Like doing drugs
You'll find some drug use, weed, and MDMA in the dance, but not by far are the majority doing that.
>Have a fursuit
Seems to me that around 20-25% of congoers have a fursuit. You'll have plenty of fun without one. But by all means see the suit parade, where you can marvel at the artistry of good suits, which can really be amazing... and snicker at the ones that look like the owner made them over the weekend in his garage, with a pound of hot glue and 500 zip-ties.
>Without the things above is there anything to do there basically?
Besides panels? Lots and lots and lots of socializing. Blows the stereotype out of the water. You'll find people sitting and chatting in parts of the lobby, and wherever people go to smoke outside, lots of non-smokers will congregate there. Walk up, ask a question about someone's badge or outfit or something, and slide into the group.
I haven't been to UK furcons, but at least in the US-- a kid can go, accompanied by a parent, but it's quite rare-- public lewdness is kept down by staff. You'll likely find the same thing there. X-rated stuff must be kept covered in the dealers' room, and staff will put the kibosh on anyone wearing skimpy clothes or getting too handsy in the lobby areas (including those areas where one must have a badge to enter), though both of those do seem to be uncommon.
At night, there are usually social gatherings in people's hotel rooms. There's usually alcohol, but nobody minds if you don't drink. People chat, talk about art and the fandom and other things, and just be chatty. Depending on the con's, and the hotel's, rules, some gatherings may put a sign on the door-- you can knock to get in-- or even leave the door open. I'm really into room parties, and I end up in a lot of private, closed-door ones; in 19 years and maybe a few hundred of these, I've seen sex twice ("Oh, someone's getting a BJ in the corner") and random nudity an additional once.
I have one big, all-important piece of advice for having fun at a con: as best as you can, toss all your preconceived notions (drugs, must have a fursuit, public lewdness, etc.) out the fuckin' window, go in with as open a mind as possible, and relax. Those preconceived notions can prevent you from having fun, if you're convinced that, because of those factors, you won't and can't. If you go in thinking everything will be shitty, you absolutely will not have any fun, because you already 'know' you won't. Similarly, going in with a pin-point focus-- something I hear occasionally-- is just as troublesome; if you don't get what you came for, no matter how much fun you had, it'll seem as though everything sucked.
P.S. There are straight furries without kinks. Might be uncommon, but they certainly exist. But I think cons aren't the place to hunt for that.