Our main business contact with charities is through buying stamps in bulk, but over recent years many organisations have found that collecting coins can be very lucrative. (Many of the charities from whom we buy stamps and coins find that the coins now more than match their stamp income.)
In broad terms, coins and banknotes break down into categories as follows.
COINS
Coins current in other countries, or recently current. This includes some of the "legacy currencies" in use in the Eurozone countries (Austria, Germany, Ireland, and Spain are still ok - others are now demonotised, and we only buy them as scrap). Many members of the public have little bags of leftovers from holidays and business trips, and are now quite happy to give them to charity.
Coins of collectable value. This for a charity can be difficult to sort out from other scrap/"smush" but we do the separation for sellers. Sometimes a charity might be donated an organised collection, in which case this would be worth keeping intact in case it includes any better items.
Coins of low value. After the two previous groups have been extracted, this is what is left.
BANKNOTES
Banknotes current in other countries, or recently current. The notes above for coins apply here also (but many of the notes from Eurozone countries who's coins have been invalidated are still acceptable). Remember that there are many notes that a bank or bureau-de-change might tell you cannot be exchanged, but that can; we'll identify everything that can still be exchanged,
Other banknotes. All banknotes have some collectable value, although the cheapest (either very common, or in poor condition) are often worth only a few pence each. It is very important that any notes you are given which are in mint condition are kept that way.

PRICES
On the current coins and notes, and the €uro legacy currency coins and notes, we pay on average about half of the current exchange rate. Prices tend to be higher for batches which have higher quantities of larger denomination coins, or with larger numbers of notes. Lower prices are earned by lots with concentrations of very low denominations. We do not have fixed rates; we tend to build up a longer term trust with our suppliers.
We sort through the other material and make an offer depending on what is there. (Sorry - that's a bit vague !  Unfortunately there is no way of fully explaining this aspect of pricing without possibly misleading.) However, we can always break prices down, and explain how our figures are arrived at, and everybody has the option of turning down our offer. More information.

SORTING
If you intend to bring such material to us for sale, it is sometimes useful to sort it first. Cutting down on our work often means we can pay a better price. Certainly keep the banknotes separate from the coins. With the coins, it is worth sorting into countries (don't bother with smaller batches of less than, say, 100 coins of mixed countries). It is ok to have mixed denominations in bags sorted simply by country; we only welcome sorting by face value when large quantities are concerned. Remember - we would rather be faced by a mound of loose unsorted coins than by a box of coins all neatly wrapped and labelled, which just takes lots of time to look at.

PAYMENT
We normally pay on the spot for batches brought into us (but you need to make an appointment). Large lots might need to be left with us for checking and counting, then you can either come to collect payment or have a cheque or bank transfer sent to you. We like to have forewarning of very large lots (i.e. of about £500+ sale value - by a rule of thumb, this is about as much as a strong and healthy person can lift in one go !).