Spot the problem: the loft

1. Daylight through the roof. Where light gets in, rain does too. A slipped or broken tile usually sits above it. A roofer.
2. A damp stain on a rafter. Dark staining means water has been getting at the wood, from a leak or from condensation. A roofer to check the roof above it. If the wood feels soft, a surveyor can look at the timber.
3. A bird's nest by the eaves. A nest shows there's a gap birds can get through. It also blocks the air at the eaves. If birds are still using it, wait until they've gone. A roofer can close the gap once the nest is empty.
4. Insulation stuffed into the eaves. The loft needs air coming in at the edges. Blocked, condensation builds up and the timbers get damp. An insulation installer can fit eaves trays that keep a gap open.
5. Gaps in the insulation. Heat escapes through every bare patch. The usual recommended depth is 270mm. An insulation installer, or you can lay more rolls in the gaps yourself, wearing gloves and a mask.
6. Boxes squashing the insulation. Insulation works by trapping air. Squashed flat, it keeps far less heat in. You can sort this one: move the boxes off it. A carpenter can fit raised boards if you need the storage.
7. A cold water tank with no lid. Dust, insects and worse can get into the water, which may feed your taps. A plumber can fit a proper lid.
8. Pipes with no lagging. Water pipes in a cold loft can freeze in winter and burst. You can fit foam lagging over them yourself, or ask a plumber.
9. An old grey flue pipe. Some older flue pipes were made with asbestos. Left alone and undamaged, it isn't a danger. Leave it alone. An asbestos surveyor can tell you what it is before any work near it.

Only looks wrong: the lining dipping between the rafters. The membrane under the tiles is meant to dip a little, so any water that gets past the tiles runs down to the gutter.