Do like we said first! For the price of either from FIAT you can join ClubCento, gain access to Rallycinq's secret test proceedures to verify the integrity of the SPI sensors. and get yourself mega discounts from Fluffy the Impaler.
In short, about £20 a hit. Which is a bit more than a compression tester.
Haven't found anyone who have as many items at such competitive prices where you can buy on line and get with a few days at most, or pay more for next day delivery.