FX Differences on revenue

 Any suggestions on how to best handle FX differences arising in the following situation:
Currencies
- Functional currency / Project currency = GBP
- Funding Currency / Invoicing currency = EUR
- Invoice Processing currency = Funding currency
Project setup
- Funding = £1 soft limit
- Dist rule = event/event

Month 1 - invoice event:  EUR 15,000 @ 1.5 = GBP 10,000 paid in same month at same exchange rate(ie no gain/loss)
Month 1 - revenue event: EUR 5,000 @ 1.4 = GBP 3,571
Month 2 - revenue event: EUR 5,000 @ 1.3 = GBP 3,846
Month 3 - revenue event: EUR 5,000 @ 1.2 = GBP 4,166
Total revenue = EUR 15,000 = GBP 11,583

So the funding in funding currency is fully used (EUR 15,000) but there is still a UBR/UER balance in project currency of GBP 1,583