To be honest, I am a little bit amazed that so many people on a UK forum have ordered a gasoline engine. Reading mostly UK automotive websites (for the simple reason I don't speak any other European languages besides English and my native Bulgarian) I am under the impression that you Brits drive mostly diesels due to taxation favoring low CO2, fleet cars policies, etc. I believe gasoline cars are more popular in mainland Europe.
Speaking of taxation policies here's some curious offtopic: in neighboring Greece there was some odd policy to put very low taxes on cars of 1.3 liters or lower displacement which made the Mazda RX-8 190PS (1.3 rotary Wankel engine) very cheap to own
It boils down to cost for most, yes. Resale values tend to be higher, tax lower and lower consumption for the diesels. However, when new, unless your do the mileage to offset the difference in price of a diesel vs the equivalent petrol - In the case of the FR 184 TDI vs the FR 180 TSI, the TSI is £535 cheaper - at a difference of 4 pence per mile between the economy of the TDI and the TSI, that's nearly 13,500 miles before you claw that money back. Not a
problem if you do 20k+ a year, but if you are buying new and do 6k a year, have some fun, buy the petrol!
With the stop-start systems, petrols are becoming cheaper to tax however with our tax system being in bands, there is a £105 jump between bands B and E which the TDI 184 and TSI 180 fall into - some people are swayed by something like that which is a false economy as what you save on the tax, you would have spent in the extra price of the TDI which you may/may not get back from your annual mileage.
The greek policy is something I've heard of - similar to one in Italy where it was cars over 2.0 Litres I think? Not sure if it still stands but that's why you see some classic motors with 2.0 V8s and others with 3.0 V8s putting out the same power. Madness!