Yet more drain questions.

[Wingedharpy]

Briefly:
Anyone had experience of having external underground drains re-lined?
Any companies you'd recommend ?
Any drain equivalent to "gas safe engineers" , or member of any regulatory body type organisation ,that I should be looking for?
Any specific paperwork or documents I should get on completion of work? (Like equivalent to FENSA certificates for windows).
Finally, can drains be relined at this time of year?

Any drain engineers about?....please.?

@PigletJohn might be able to help you @Wingedharpy

Interested in the response here

Thanks @WhoppingBigBackside.
I didn't like to put a call out for PigletJohn, though I did think of him/her.
Poor soul must spend half his/her life on here answering queries from frantic householders, but given that there are now 2 of us wondering (waves to PlumManor), @PigletJohn, are you there?
Help!

sorry, I have no knowledge of drain lining.

No worries, PigletJohn.
Thank you for posting.
Back to the drawing board.

My apologies PigletJohn and Wingedharpy

The water companies do reline drains if they are classed as public sewers on private land eg serve more that one property, if there are repeated blockages.
I haven’t had any drains relined as both times I have had drain problems in houses I dug them up and replaced them with plastic on my land despite them being public sewers in the sense of serving more than one house.
The second time I did this was because due to a blockage that the water board cleared, they found during the camera survey (which he kindly did on the private drains as well and the public) there were many dead ends which needed sorting.

Thanks for your input @mayblossominapril.
There are no blockages at all here at Wingedharpy towers - just old glazed pipework that have some cracks, but are still functioning, albeit, most likely, leaking a bit.
Advice from CCTV drain survey was to reline 2 drains at rear of property and dig up and repair 1 at front of property.
My dilemma is, how do I choose a reliable company to do this work ?
Is there any sort of paperwork/certificates I should be asking for, in the event I may need to produce this as evidence should we sell house in the future?

You could ask your local building control. I don’t think it falls under building regs but a phone call or email to a building inspector might give you a bit more info.
I suspect the water companies contract out drain lining as they seem to contract most things out so a contractor they use would probably be best. If you see them digging up the road somewhere and they look friendly you could ask them.