Serves you right for being so rich Mark
If it were me, being a perfectionist, I would have to take the tank out and see.
However, I'm sure there is no hurry. Coins can't block the oulet or filter.
Some chemist will be along shortly to tell you what effect ratty UK coins in Tesco's Finest will have on the RON etc.
There's a bit of me that thinks ignore it and having tried getting even crud out of an old Honda tank before now, the seemingly simple becomes the obviously impossible. The filler would have to come out anyway.
You could wait for the tank level to drop, whip the tank off, drain it and shake it to hear if anything is rattling around in there.
Brian (who, like HMTQ, never carries money, couldn't get himself in your position as credit cards don't fit throught the filler neck
)