Land drainage into manhole

[earthwagon]

My patio floods with 5-8cm of water when we have heavy rain. There are no drains on the back of my house. I'm on clay soil, so soakaway won't work. So I've dug a trench which runs along the house side of the lawn, across the patio and down the side passage to the combined SW/FW chamber. It's quite a small chamber, about 65cm by 50cm. I'm intending to lay membrane-wrapped perforated 80mm pipe along most of it, with a short length of solid pipe incorporating a trap, entering the chamber. I read on another post that the solid pipe should be 110mm. If so, are there adaptors to connect 80mm to 110mm or do I have to get 110mm perforated pipe too? And do I need to get Building Control approval before I drill/break into the chamber? The depth from path to the top of the benching is only about 18cm. I'd rather not have to break into the benching if possible.

[earthwagon]

Overwhelming response. Thanks.