By Antony Clements-Thrower A terrifying 750-mile wall of water is set to collide with the UK this week, with Brits warned to expect around 6mm to fall every hour. Weather warnings for rain have been issued by the Met Office, with most of Northern Ireland, south Wales, as well as Devon and Cornwall. The deluge is expected to start this afternoon (Monday) – but will linger into Tuesday morning when flooding is likely as a result of the downpours, forecasters warn. The rain looks all the more terrifying when seen as part of the Met Office ’s weather map for Tuesday morning. Stretching from Dover …