If you're going outside their terms and conditions I'm guessing that means you're operating in a high-risk sector so your best bet is either to go with a payment provider that specialize in your sector (they'll have risk models that can handle your situation better) or get a merchant account directly (they'll probably ask that you put down a significant deposit to mitigate the risk)

Thanks for the insight. I've done some asking around and it sounds like a lot of the UK payment provider restrictions are actually due to the merchant provider they use; there's a possibility that I could use any UK provider as long as I negotiate my own merchant account directly with a bank.

SagePay (sagepay.com) is one option, it also integrates with CheddarGetter (cheddargetter.com)

Without more information this is going to be impossible to answer.

Impossible? I'm not asking for a personalised quote here, just what options are available to UK startups. I probably clouded the water by mentioning my personal situation, but really I'm just interested in what's out there.

Ukash allow gambling and adult. Awkward but legal.

Also if your starting a gambling business then payment providers are the least of your concern. You need to be licensed by the UK gaming body - http://www.gamblingcommission.gov.uk.

I'm hoping to avoid e-wallet style providers, but thanks for the tip, I'll make a note of them.

And yes, licensing is a problem for another day. The UK's gambling laws are complicated and vague, especially when online businesses come into play (it all seems like an after thought, as always). I think we've got that one covered though.

I wouldn't say the UK gaming law is vague but it is complicated.

Basically unless you're a charity you'll need to be licensed.

Not necessarily; and this is what I meant by vague (though yes, complicated is probably a better term).

http://www.gamblingcommission.gov.uk/gambling_sectors/remote...

  Do I need a licence if I am based abroad?
  
  You do not need a licence from us to run a remote gambling service if all of your
  remote gambling equipment is located outside Great Britain.
  
  If you are based abroad and want to advertise your gambling services in Great
  Britain, you must be based in a whitelisted country or a country mentioned
  in the Gambling Act 2005.

What qualifies as our "gambling equipment"? Our webservers?

That being said, it's still probably a good idea to get a license.

FastSpring (fastspring.com) seems pretty decent.

Yes they do. I investigated them too, but sadly we also violate their terms and conditions.

Could I ask what it is that you are doing that violates the terms? Just out of curiosity...

My app falls into the rather broad category of "gambling, gaming, and adult". This means all US providers (I've seen) aren't interested due to their gambling regulations, and UK providers consider it high risk.

So what do your competitors do? I know it's an obvious question... but it's probably also the answer to your problem.

Pay more money than I'm probably willing right now... :)

Seriously though, our competitors seem to do it themselves. Which probably means PCI compliance and a merchant account, then doing all the integration themselves.