As these have appeared since you checked the earths, I would be inclined to recheck them and carefully examine the terminal as it connects to the cable, as it may be breaking up or solid in green crud where the crimp rolls round the cable end. Take them off again, give the terminals a good soaking in WD40 once they are off the body, clean the body area around the mount hole in a radius of about 5mm with some fine wire wool. Give the terminals a go over with the wire wool too so they are clean and bright. Once you put them back on, cover them in some Vaseline AFTER they are tight.

 

If the earth point is a bolt hole like mine, get a similar old bolt, cut a shallow groove along the threads and then run a nut back up it to make sure it still works as a bolt. Remove the nut, and run the bolt carefully down the threaded hole to clean up any crap in the thread itself.  This youtube link should give you an idea of what I mean - https://www.youtube.com/watch?v=iuSk53cMsFk

 

You could also check the earth point on the scuttle panel under the wiper covers near where the ECU lives.

 

Before I touched the earths the tcl and abs were on and staying on. I didnt scan at the time hoped the clean up would sort it. This was the first ignition cycle since pulling the fuses out for exam. Where the earth cables were crimped they weren't too bad for green crud, managed to clean most of it off as well. I'm hoping for good weather for a whole day so I can get amongst the abs sensor to check the module plug. Looks like TIP airbox and a couple of other bits need to come off for access. While I'm pulling all that off will double check under the battery. Will have a look under scuttle panel too. Car started fine, engine ran and cabin electrics seemed fine, I didn't drive it, the flashing handbrake light was a bit disconcerting.

Oh and I'm not sure the tcl came on at all last time I tried ignition, after clean up only abs stayed on, like I say I'm not sure tcl came on at all.

Oh and my earth points are a threaded stud sticking up, capped bolt screws on. Did my best to make sure inside bolt and thread were clean.

In that case, looks like either the connector block is faulty because of corrosion if you're lucky, or the ABS ECU has cashed in its chips.

 

I would start to check out if anybody has one of these on any of the breakers in the for sale section as these do not come up every day of the week and may be difficult to source.

I'm thinking that too. I've seen some have cracked them open and resoldered cracking pins, not a task for the faint hearted and not really one I'd like to tackle. Is it safe to assume it is a problem at the abs end given I'm able to do a full scan of ecu and communicate with everything else? Is a fairly common fault apparently on older bosch abs units. I can replace that without bleeding the unit? Would a replacement module need coding?

I'm afraid I've never got that far involved in one, so can't answer yes or no to that question. However, below are links for everything you should need if you decide to get adventurous. I would suggest maybe getting a little extra info from a few more sources on here before steaming in. Tech1e has been helpful to me on here in the past, so may be worth a pm.

 

http://workshop-manuals.com/skoda/octavia-mk1/chassis/abs_adr_tcs_edl_esp/electrical_test_abs/edl/_tcs_mark_60/multi-pin_plug_connections_with_contact_assignment_for_abs_abs/edl/tcs/

 

http://workshop-manuals.com/skoda/octavia-mk1/chassis/abs_adr_tcs_edl_esp/summary_of_components_of_hydraulic_control_unit_brake_servo_unit/master_brake_cylinder_for_vehicles_with_abs_abs/edl_mark_20/

 

http://workshop-manuals.com/skoda/octavia-mk1/chassis/abs_adr_tcs_edl_esp/electric/electronic_components_and_fitting_locations_abs/edl/esp_mark_20/repairing_the_hydraulic_control_unit_abs/edl/esp/

Cheers Phil, I had the module plug off today, a bit hard to see the male pins but looked ok and no signs of any problems on the female block. Remaking connection also made no difference. Think I'd be looking to book it in somewhere to fit a used one but to be honest the to do list on this car never seems to get any smaller, I need something I can use daily and don't have much time to sort it out so I'm weighing up my options at the moment. Thanks again for all your comments and advice. Think we got to the problem but I feel it's just one too many at the moment.