I don't think it is unusual to have a small number of quotations. We have had the same problems from time to time. Sometimes it's Hobson's choice.
I presume you have tried to get three quotes?
There is no requirement to accept the lowest quote either, often we decide on local knowledge of the councillors, along with how detailed the quotation is, in respect of what the contractor is promising to deliver. Often a very high quotation means that they don't want the job!
IIRC any contract over £25,000 must be advertised on the “Contract Finder” website (Public Contracts Regulations), so you are exempt from this.