Wiring confusion when replacing central heating timer.

I've been meaning to replace my central heating timer ever since I moved into my house last year, and recently got around to buying one. Now that I've tried to actually do it though, I've hit something of a stumbling block...

I've bought a Danfoss TS715-Si to replace an ACL LP111. Wiring diagrams for each can be found here and here respectively. According to the wiring conversion chart in the Danfoss's instruction book, all I have to do is use the existing backplate but swap terminals 3 and 4 over.

Trouble is, when I took the old unit off the backplate, I was confronted with this mess. Far more wires than I'd expected, none giving any real clue as to their purpose. And nothing wired in to terminal 2 - there should be, if the wiring diagram is correct. But the heating has always worked fine with this timer - I'm only replacing it because I can't stand not having a "+1hr" function.

If it's relevant, my boiler is a Worcester Bosch 280 RSF.

Any help would be much appreciated, as I would really prefer not to have to get a professional in for this if I can help it. Thanks in advance...

why not follow your own instructions? (ok so you only have one wire in 3 put it in 4 and put the new timer on, if that doesnt work put the wire back, oh and its not a mess

I suppose I could just swap that single wire... I just didn't want to risk damaging the new unit.

I suppose I didn't really mean 'mess' as in 'shoddy work', just the fact that there was a lot more behind there than I was expecting. I expected one wire each to N, L, 1, 2 and 3 (plus earth).

Okay, maybe my problem is I should have more confidence in myself... it worked fine just by moving that single wire from 3 to 4. Thanks.