This seems like very poor service and could be described as harassment. I work for a secured lender (not firstplus) and we would call to confirm the paperwork was recieved and then call in a few days to see if you've made a decision, if you havent we would arrange a time to call, and stick to it.
What FP are doing doesnt give a good impression and not all companies are like this. I would reccomend looking at some of the other providers on this site and give them a call, mention that you have a quote with FP and they will probably better the rate too.
Only explanation for this from FP is the possibilty that the loan consultant needed this fir his monthly targets and commission or that FP really need the business as they have had problems with their arrears department and were not collecting the debts but just writing them off - this means they have lost a lot of money which they need to recoup. This has also led to their new premises being indefinately postponed and a freeze on staffing increases.
HTH