Santander's takeover of 318 RBS branches is not expected to be completed until the first quarter of 2012, despite hopes the deal would be done by the end of 2011.
Gross mortgage lending in March was an estimated £11.3bn, a 21% rise from £9.3bn in February, according to CML data.
Coutts, the private banking arm of RBS, has changed its lending criteria for mortgage clients who will need to have £1m of investable assets before it considers applications.
Nationwide Building Society has announced it is to restrict the maximum LTV of its interest-only mortgages to 75%.
Mortgage borrowers are set to get more protection under new EU draft proposals unveiled today.
About 70% of brokers say the average amount of commission they earn per product has fallen in the past year, research suggests.
Northern Rock is set to offer 90% mortgages, just three years after it was bailed out by the taxpayer.
Almost 60% of buyers opted for a fixed- rate purchase mortgage during 2010, with more buyers expected to choose the product this year, new research shows.
UK banks will not increase mortgage lending this year as extra regulatory pressures and a lack of funds continue to restrict the availability of finance to borrowers, Hometrack says.
House prices fell by 1.3% in December, and may extend their decline this year as uncertainty over the economy continues to deter homebuyers.