SELECT prop.id,prop.datesubmitted
       ,cust.forename,cust.surname
       ,cust.tradingname,prop.quoteterms
       ,prop.customerref
       ,v.vehicle
FROM   tblProposals prop 
LEFT JOIN tblCustomers cust ON prop.customerID = cust.ID 
outer apply (
       select top 1 v.vehicle
       from   tblVehicles v
       where  v.propid = prop.propid
       order by v.vehicle
       ) v
WHERE prop.proposalstatus=2 
AND    prop.userid='test@test.com' 
AND    (prop.customerref LIKE '%qash%' 
       OR prop.id LIKE '%qash%' 
       OR v.vehicle LIKE '%qash%')