thumping noise - pipes?

[frankief]

This is a good one. From about 11pm onwards this starts - sounds like a boiler or pump. Thump, buzz, buzz, rest..thump, buzz, buzz, rest..repeat etc. Ok I thought - eliminate one by one. Turn boiler off, turn water heater off, turn gas off at mains, turn water off at stopcock and drain system..Still it continues! Turn electricity off at mains, disconnect wash machine and dish washer, isolate electric shower feed, bleed radiators..still it continues! Isolate gas fire etc.
Investigate loft - no plumbing up there anyway but i'm desperate - there is an old wasps nest but it's definitely a machine made noise I hear.
Next I tackle my neighbour (I live in a semi) - she just had a new bathroom put in, but just sanitaryware i'm told and she cant hear anything, anyway she's a good neighbour.
Any thing that I have missed?, i'm either:
1. Going mad - but the noise is maybe disguised by TV/ life during daytime.
2. Somebody is transmitting soundwaves into my house from aross the street! CIA?
3. I have a hearing defect - going for a check up but dont think so.
Any ideas please pass them on to me.

[Ethel]

Can you hear it if you wear ear plugs?

Are you near an electrical sub station?

Are you near to any premises that has an industrial air conditioning or refrigeration unit?

[weeal]

Does your neighbour have a R.Rabbit with faulty batteries? lol

[terence7556]

did you notice the noises after the neighbour had the bathroom work done

[oldmegan]

Sounds like an airlock in pipes, or otherwise an old boiler that is caked up. I know you said you had turned stuff off, but sometimes the noises can last afterwards. You sound desperate. Sleep outside in the garden shed!!

[frankief]

Thanks for your answers.
I can just about cut the noise out with ear plugs but its a low frequency throbbing which is particularly repetitive!
No substations or aircon units near.
I used to notice this sound late at night when in the spare room on the computer, before the neighbours work was done. However, it never stopped me sleeping and seems to be worse now.
Airlock? I've had one of those and it was more a banging/clunking than a droning noise. The boiler has been off for a month now, I will try turning the water heater off for a few days.
My latest theory after a weekend ripping off pipe boxings is the chimney/ wind downdraught but that wouldn't give such a regular pattern sound I reckon.