Hucknall to Hawarden W/V is stated as 260/15 Tas 85kts Var 5W
I dont really understand where they get 5W from but thats what it says in the book.
Actually the real variation over there is more like 3 to 3.5 degrees west. You can find this on the map. On the ICAO one that I have the isogonal lines (the lines that connect points which have equal variation) run roughly NNE-SSW and are dashed blue. If you don't know where to find this information in your map, first look in the legend for the words "isogonal", find the corresponding symbol and then look for them in the map.
But we'll assume the given 5 degrees west for the rest of the calculation.
My answers are as follows,
Highest spot elevation (not obstacle) I found was 1657 near D304, so 3000 seems to be correct.
279 if I measure it. That, of course, skews the whole rest of the calculation.
HDG T 281
DIST NM 64.5
If you assume that 285 is correct (for the sake of argument), you should be getting:
DRIFT 4 west (from the flight computer)
TRUE HEADING 281 (=285 - 4)
MAG HEADING 286 (=281 + 5)
GS 72 KTS (from the flight computer)
TIME 53.7 minutes
If you assume that 279 is correct, the numbers are very slightly different:
DRIFT 3 west
GS 71 KTS
TIME 54.5 minutes
Hawarden to Manchester
Stated W/V 280/20 Tas 90kts
633 spot elevation near Macclesfield. So correct unless we both missed something.
TRK T 067
HDG T 060
So far so good. But how do you get from TH 060 to MH 072? The difference between the true and the magnetic heading is the variation. So even if you forgot which way the 5 degree variation went, the MH should be either 055 or 065. In this case, the variation is 5 west, so the MH is 065.
More like GS 101 on my flight computer.
If you assume GS 101, then 27.5 nm takes 16.5 minutes. If you assume GS 106 then 27.5 nm takes 15.5 minutes.
So... Looks like you need to re-read the unit once more, particularly how magnetic variation influences your true heading. You did that wrong twice. And you need to re-read the notes that came with your flight computer, because you are making some basic calculation errors in your GS/DIST/TIME calculations.