Well I do have soldering-skills, but pretty basic.

It depends a bit how the wiring looks like, if there's no room for scotch locks, I would maybe soldering the new wiring in place, if I wouldn't risk burning any sensetive parts up in the process :p

The loom in the lamp connector areas is usually wrapped in tape leaving 5-10cm of cable visible for individual colours. If you can't get enough space for scotchloks, just cut a few cm of the insulation wrap tape back till you have enough room and re-wrap with electrical tape afterwards.

On the mk1 octavia the original indicator relay was not powerful enough to handle a trailer load as well. When a towbar was fitted they would fit a new uprated relay as well.

I believe they eventually discontinued the original relay and only sell the uprated, but may be wrong on this.

Sounds to me as if the trailer lights are wired up wrong, and that as blown a fuse for the indicator circuits....  (the faster ticking of the indicator relay relay suggests no power to the bulbs - hence it flashing faster to indicate a failed bulb (or 3!)