Gouping By And Suming Calculated Fields In A Query

I have been given the unenviable task of processing data from a 700,000 line database. As an seasoned Excel user but absolute Access beginner, I've managed to handle some of the simpler data requests but the latest request has me somewhat stumped. The problem is as follows:

The fields are:
[Loan]
[Valuation]
[Type]

I have created a query that calculates two fields based on this data:

i) [LTV] = [Loan]/[Valuation]. The code I have used for this is:

SELECT IIf([Valuation]=(0),Null,[Loan]/[Valuation]) AS [LTV]

ii) A percentile reference [P Range] calculated using the following code:

IIf([LTV]>0 And [LTV]<0.1,"P0",Null) & IIf([LTV]>0.1 And [LTV]<0.2,"P10",Null) & IIf([LTV]>0.2 And [LTV]<0.3,"P20",Null) & IIf([LTV]>0.3 And [LTV]<0.4,"P30",Null) & IIf([LTV]>0.4 And [LTV]<0.5,"P40",Null) & IIf([LTV]>0.5 And [LTV]<0.6,"P50",Null) & IIf([LTV]>0.6 And [LTV]<0.7,"P60",Null) & IIf([LTV]>0.7 And [LTV]<0.8,"P70",Null) & IIf([LTV]>0.8 And [LTV]<0.9,"P80",Null) & IIf([LTV]>0.9,"P90",Null) AS [P Range]
FROM [BASE TABLE]

I suspect this code is somewhat clumsy but it is the best I have managed so far!

My difficulty is creating an output in the query

First the outputs need to be grouped by [Type] and by [P Range]. Then I need the following other outputs
Count[P Range]
Sum[Loan]
Sum[LTV] in each subgroup

I tried adding a Group By to the query in the design view, but I get an error every time. How do I output this data?

I have tried to read up on this but haven't managed to create a successful query!

I've attached a simplified version of the database as an example and to show where I've got to with this query

Please help!

Thanks

Oli