Foreign Currency in CT Return

I'm starting to do some gig work for a company that pays out to Paypal in $US. This is converted to GBP in Paypal and withdrawn to a UK business bank account.

I trade as a Ltd co (no other employees or officers) and until now I've been filing CT return micro-entity accounts using the HMRC online system (with simultaneous filing to Companies House). Accounts are very simple, mostly just income and sundry expenses like stationery, travel and web hosting and the filling takes me little more than an hour. I work from home but I don't bother claiming for electricity, etc. So I've been keeping my transaction records and accounts in Excel spreadsheets.

I known that the online HMRC system can't be used to file where there are foreign currency transactions.

Any suggestions on the cheapest option to restructure my filing? I don't need an industrial strength Sage package or the like and I've managed until now without an accountant.