Minimum time for Heathrow connection?
 

Hope someone can help me out, and thanks in advance.

I will be travelling to Switzerland via London in March next year. The itinerary planned is:
SFO to LHR (arrive 11:25) by United Airlines, then connect to:
LHR to ZRH (depart 15:35) by British Airways.

Will 4 hours be enough time? The 2 flights will be separate ticket purchases. Does that mean I will have to go through arrivals, retrieve my checked bags, transfer to another terminal, check in my bags again, and go through security?

The reason I will have to connect is my overall trip will be to Switzerland first, then to the UK, then fly home to San Francisco (If I booked a one-way ticket from SFO-ZRH, then another one-way LHR-SFO back, the prices are astronomical). It's just a ton cheaper to do a roundtrip ticket SFO-LHR, and separate ticket LHR-ZRH.

Welcome to FT!
Search is always your friend for a question like this.
The Heathrow website is very useful http://tinyurl.com/2gmveq.
Also if you search this forum using "Heathrow connection" you will find multiple threads, including this one from the other day http://www.flyertalk.com/forum/u-k-i...t3-t1-lhr.html
The MCT for T1 (UA flight arrival) > T5 (BA flight departure) is 90 mins.
Four hours should be plenty of time. UA and BA do interline bags. I suspect UA will interline your bags from SFO-ZRH on the outbound. But BA may not do so on the return as you're on separate PNRs. Be sure to leave plenty of time to connect on the return.

Welcome to FT!

What you're proposing to do will work, but there might be a better way to do it.

Rather than booking two one-way fares, look for an open-jaw ticket. This means you'd be able to book SFO-ZRH and then LHR-SFO as part of the same itinerary. If you book via someone like Travelocity (use the 'multiple cities' flight search option), they'll even be able to sell you the tickets on different airlines - eg Swiss for the outbound, and United back. Picking some random dates in March, I'm seeing fares that are around the same as an SFO-ZRH return.

If your itinerary isn't fixed and you're trying to squeeze the costs of your flight down, then you might want to consider doing London first, then Zurich: UK Air Passenger Duty for long haul flights costs more than equivalent Swiss departure tax.

You can then go and use a site like SkyScanner to look for a decent price between London and Zurich. There are a handful of airlines on this route, but bear in mind that easyJet and AirBerlin will charge extra for checked-in baggage.

(If you're feeling brave, you could use the 'multiple destinations' search to book all three tickets in one go; but that can push the price up somewhat - so it can be better to book the middle leg separately)

That's plenty of time to connect. Even though the airlines probably won't interline your bags, you should not have any issues.

It should be possible to get a ticket from SFO-LHR-ZRH with a stopover on one leg in LHR, although the cost of that could be a bit of a wildcard.

In coach on this route the cheapest BA fare basis allowing a stopover is LLXE2NA, which allows it for $100, but that's $840 more than OLX7Q2Z1, the overall cheapest.