Same as any investment - fiat, bonds, stocks, shares - pay your taxes and you will have no problems, provided you aren't doing anything illegal.
Not really the same, because stocks and bonds can't be sent in the same decentralised and pseudonymous way that BTC can.
I don't think that the UK government really considers crime conducted with BTC to be as huge a threat as they claim - if anything the threat may be decreasing, because small-scale criminals can often find the fees annoying (as you can tell on darknet markets and related forums).
They should really be focused specifically on taxation, but instead they're pretending that crime is a huge factor in their decision. Even though it may play some part, I think that the prominence of P2P trading and the use of cash makes this a futile battle.