I have just fixed a similar problem on my Mk2 Octavia Estate. I replaced the catch on the hatch back, checked for broken wires where they come through the body into the tail gate, replaced the soft touch switch under the number plate and bought a new actuator which fits onto the tail gate latch. All to no avail, the boot still wouldn't open. What i did then was test the new actuator and that was faulty, I paid £10.50 from a e bay it must be junk, so I bought a genuine one from the Skoda dealers in Ellesmere port £25 complete with the latch, and hurrah the hatch now opens. If any one reading this has similar issues these are the four main things to check.