If you are in a fixed rate you should consider a top up with your current lender. You will probably avoid legal fees also by staying with your current mortgage provider, although this depends on your lender and/or top up amount.
You could, however, avail of a better rate based on the LTV if you switched lenders. This requires a solicitor but some lenders are now covering this cost. Also, bear in mind that a penalty will be apply if you are currently in a fixed rate.