With forecasts spelling out an incredibly hot few days, rail operators are already stating that they envision a number of services being disrupted, with some delayed and others cancelled. This could well be at very short notice. As such, other forms of transport, including buses, could very well be much busier and crowded.
Please ensure that you keep up to date with the situation by either checking the rail operators' websites and social media channels or Network Rail's status checker, especially before you're planning to leave.