250 feet looks about right for most of the low level runs we see around here- I know its very hard to judge and I was right underneath this one, Also I was on top of an upslope from the low lying area south and west of Frome and it drops away again just to north east of Frome where there is nice railway and power line to follow.
So thanks for replies , I would hazard a guess he was probably a little between the two figures and as I said very spectacular at that height and speed. and its a big-certainly wide-bodied - plane presumably so it can take a modern tank where a herc could not?