Oh dear, yet another "satnav assisted PCN" !
We see so many of these nowadays where drivers seem to obey the instructions like automatons and ignore roadsigns. Looking at your case though, the signs do seem to be excessively high, and a recent (yesterday) case at London Tribunals on this very subject was won. So there is hope.
Other thing to check on is the presence or absence of advance warning signs. Unfortunately GSV is out-of-date here so doesn't show the restriction signs, which means it won't also show any advance warning signs. So if you want to build a robust appeal case, you'd need to do some legwork to find out if there are any advance warning signs of the restriction.
There may be a 'technical' appeal based on Grenwich mismanagment of the enforcement process. Such appeals are not related to the allege contravention so can win even if the contravention is made out. So wait a bit to see what may be suggested, but don't miss the deadline to pay or appeal on the PCN.
