When this get put into play properly every agency and their dog can take a gander at your browsing habits without a warrant (and therefor without probable cause):
- Metropolitan police force
- City of London police force
- Police forces maintained under section 2 of the Police Act 1996
- Police Service of Scotland
- Police Service of Northern Ireland
- British Transport Police
- Ministry of Defence Police
- Royal Navy Police
- Royal Military Police
- Royal Air Force Police
- Security Service
- Secret Intelligence Service
- GCHQ
- Ministry of Defence
- Department of Health
- Home Office
- Ministry of Justice
- National Crime Agency
- HM Revenue & Customs
- Department for Transport
- Department for Work and Pensions
- NHS trusts and foundation trusts in England that provide ambulance services
- Common Services Agency for the Scottish Health Service
- Competition and Markets Authority
- Criminal Cases Review Commission
- Department for Communities in Northern Ireland
- Department for the Economy in Northern Ireland
- Department of Justice in Northern Ireland
- Financial Conduct Authority
- Fire and rescue authorities under the Fire and Rescue Services Act 2004
- Food Standards Agency
- Food Standards Scotland
- Gambling Commission
- Gangmasters and Labour Abuse Authority
- Health and Safety Executive
- Independent Police Complaints Commissioner
- Information Commissioner
- NHS Business Services Authority
- Northern Ireland Ambulance Service Health and Social Care Trust
- Northern Ireland Fire and Rescue Service Board
- Northern Ireland Health and Social Care Regional Business Services Organisation
- Office of Communications
- Office of the Police Ombudsman for Northern Ireland
- Police Investigations and Review Commissioner
- Scottish Ambulance Service Board
- Scottish Criminal Cases Review Commission
- Serious Fraud Office
- Welsh Ambulance Services National Health Service Trust
Not to say that some of those agencies haven't broke TLS encryption anyway, but for a little peace of mind consider at MINIMUM installing this browser extension to force HTTPS connections to supporting websites https://www.eff.org/https-everywhere%20
However, I prefer to use a VPN. proXPN get's my vote since they had a cracking lifetime deal a few years ago, but any that are not based in the UK should be a good bet. Again, some of the agencies listed above can no doubt get around that if they are determined to see what you're doing, but it would at least thwart some of the lower level snoops.
Remember the laws in NI around paying for sex. Now the PSNI do not need a warrant to keep an eye on you if they intercept your traffic to an escort related website, and you ISP has to keep 2 years worth of your browsing history by law.
IMO the around £50 a year it costs for a reputable VPN provider is well worth it to fly under the radar.