When the booklet that accompanies the DVD claims "Timelash isn't that bad!" you know you're in trouble. When the making of extra merely reels off a list of reasons for why the story was rubbish, rather than discussing the actual making of the serial, you can't be too hopeful.
However Timelash is much better than its reputation would suggest. The story is pretty simplistic but decent enough. The acting isn't too bad except for Tekker, but I don't feel I really need to comment on that. There are some scenes which are so clearly placed for padding, principally the doctors argument with Perri at the end, which serves no other purpose whatsoever. The blue android thing was squeaky and so pretty ineffective as a menacing villain. The design in the serial was also poor, the interior of the Timelash was effective only for its comedy value. The fact that the terrifying Timelash could easily be climbed into ruined the premise f its use as punishment. Also the poor positioning of the prop meant that people had to throw themselves into the Timelash rather than being thrown into it. Colin Baker was only the Doctor for two full seasons and with such a high percentage of his stories falling short of the mark you can see why he was unpopular with the BBC bigwigs, however Baker is a good actor and could have been an excellent doctor, his performance here (excepting the cringeworthy TARDIS scenes) is a highlight, the design of The Borad is also good.
Another massive problem is the glaring plot holes displayed at the end. The explanation of the Borads escape is improbbable and unsatisfactory, and the fact that the doctor decides not to explain how he prevented the bomb shows weakness in the writing.
I have to say although I have managed to reel off a long list of faults with the serial I did enjoy it when I watched it. I have given it a low rating because it is hard to give it more when so many superior stories exist. However it is a budget release and I wouldn't warn people off picking it up for a cheap price. But with Genesis of the Daleks, Earthshock, Spearhead from Space, The Hand of Fear and other classic serials being released for bargain prices maybe you should shy away from this one.