I'd say as far as value it was probably a trade up or even, depending on condition and such. A routed Spidey will still sell for $3k+ over here, while a HUO will sell for closer to $3.8k - $4k. TZ's pricing can be all over the place based on condition, I usually see them for $2.5k to $3.5k, sometimes more if their immaculate or have been restored by a known professional restorer.
I haven't played enough of TZ to compare the 2 honestly, I do own a Spidey myself and like it. It's not very deep, but I own 2 deep games already, TSPP and LOTR. I would love to put some serious time on a TZ and really learn it's rule set, as I feel you need to understand what your doing to really enjoy a particular pinball machine. Have fun with Spidey should be easy to sell if you don't get into it, of course I don't know how the pin market is over in the UK.
Oh yeah, if it doesn't already have a shaker motor, you should consider getting one and installing it. I feel it adds a bit to the game.