Odd behaviour in multicurrency txns

[Fred Bone]

[Gnucash 2.4.12 on WinXPPro-Sp3]

My primary currency is GBP. I am not using the "trading accounts" 
feature.

A week ago I used a credit card to make a payment in EUR. When the 
statement arrived this morning it showed that EUR34.80 had been charged 
as GBP29.95 (1:1.1619) but the company is now levying a "non-Sterling 
transaction fee" which in this case was GBP0.82.

I had already entered the txn using a guessed exchange rate, so my first 
step was to "edit exchange rate" which worked as expected:

Viewed in the Expense account (denominated in EUR):
Ex:Hotel:EUR   debit 34.80
Li:Creditcard              credit 34.80
Viewed in the Liability account (denominated in GBP:
Ex:Hotel:EUR   debit 29.95
Li:Creditcard               credit 29.95

I then added the GBP0.82 to the credit amount (in the GBP account), 
resulting in a third split appearing (debit 0.82), into the Account field 
of which I entered Ex:Bank Service Charge, which is also denominated in 
GBP.

However, when I attempted to finalise this, up came an "edit exchange 
rate" window, defaulting to 1:161937, and when I accepted this the result 
(in the GBP-denominated Liability account) was
Ex:Hotel:EUR            debit 30.04
Ex:Bank Service Charge   debit 0.82
Li:Creditcard                      credit 30.77
(the Bank Service Charge account shows the same)
and in the EUR account
Ex:Hotel:Hotel EUR      debit 34.80
Ex:Bank Service Charge   debit 0.95
Li:Creditcard                      credit 35.75

Note that the EUR account looks just fine, but the amounts shown in the 
GBP view apparently fail to balance.

I've now entered the "transaction fee" as a separate txn (as indeed it 
appears on my statement), but what is going on here?