That's a popular area for the Rail Replacement service - but sometimes it doesn't operate as expected. If the Rail Replacement is for the GWR service then there are usually coaches at North Camp towards Guildford or Reading. It's typically double-deckers buses on the SWR service

Sometimes, though the replacement is for South Western Railways (was SW Trains) for the Southampton or Farnham/Lines. Is this what you were expecteding in your example? It's not often that both lines are out at the same time and so rail replacements might run from Farnborough (Main) to Ash Vale and beyond. (Ash Vale passengers would not normally go through Farnborough Main - it's on the Basingstoke/Southampton service)

It's convenient to know where these stations are and plan your journey to use alternate rail transport. I've had cause to hot-foot it from the SWR service at Farnborough (Main) due to problems towards Waterloo - down to Farnborough North and the GWR service into Reading and then Paddington. Similar from Guildford if the Waterloo service has problems, take the Reading/Paddington service. Tickets are typically marked 'Any Route except Reading', this can get cancelled when there are problems on the SWR service.

I generally plan to avoid rail replacement services wherever possible, a little help from Google or the Network Rail journey planner usually gets around the problem.

As Bromptonaut says, avoid like the plague.

I work in the rail industry, and there are two types of rail replacement - planned and unplanned.

Planned take place around engineering works, and train operators have notification of these 12 weeks in advance from Network Rail, so generally they can be avoided. It is up to the train operator to contract the buses or coaches from either a consolodator who specialises (such as Fraser Eagle many years ago who went bust) or on an individual basis. Recently, Southern and its sister company Thameslink was overwhelmed when customers getting to and from Gatwick Airport were bussed to Redhill or Three Bridges. There were not enough coaches and drivers were - apparently - unsure of the routes.

Unplanned - these happen when there are emergency engineering works (broken rail, buckled rails in this hot weather,) or a broken down train that needs dragging away or a wheel skate fitting under a siezed wheel or whatever. While there may be diversionary routes, a train driver has to 'sign' a route, that's to say he is fully conversant with the location of all signals, junctions,tunnels, stations, level crossings and bridges. This is a major safety requirement, as if you have a train fire, you will want to stop where access is easiest for egress and the emergency services. It's unlike driving on a road which is line of sight.

Train operators do struggle to get replacement buses, particulary late at night when drivers have used all their alloted hours or in the morning peak or mid afternoon when drivers are working on school contracts. There.are no fleets of buses waiting for that call - it's all pot luck.

I've had the misfortune to use one late at night from Rugby to Coventry, and the driver took the M6 to Jct 3, and not the most direct route, as this is what he knows or is more suitable for a bus.

As I said, best avoided as is travelling by rail on a Sunday. Details of line closures are published on www.nationalrail.co.uk