Hi all, I think that I have read somewhere that one should not use different tapes.
Now,not that I want to swap from from tape to tape but why is it reported to be a problem,surely if it is a top branded tape there should not be a problem changing, or is it?

Seek and ye shall find (same issue with any make/model really):
http://www.dvinfo.net/forum/long-black-line/113502-switching-tape-brands-will-ruin-your-heads.html
http://www.dvinfo.net/forum/panasonic-dv-mx-gs-series-assistant/9234-brand-tape-do-you-use-your-mx-500-a.html
http://www.dvinfo.net/forum/long-black-line/70800-problem-mixing-tape-brands-z1u.html
http://www.dvinfo.net/forum/canon-gl-series-dv-camcorders/16276-my-new-used-gl2.html
http://www.dvinfo.net/forum/canon-xh-series-hdv-camcorders/172298-question-about-changing-different-brands-tapes.html
....and a zillion others.

Bottom line - clean your heads if you have any problems.
There are rather fewer brands of tape available now so the problem is less of an issue than it used to be :-)

Use the Google search box at the bottom of the page.

Different tapes tend to have slightly different characteristics and will leave slightly different deposits patterns on the tape guides, etc. When you change tape brands, there may be a slightly different tape wrap around the tape path and the deposits from the old tape may break-off and clog the heads. This is not guaranteed to happen, but it might.

In the 1990s there was an issue with incompatible tape lubricants, but that was resolved in the 1990s. Should not be an issue today, unless you find some V E R Y old Sony tape stock.

Many users do find a tape they like, buy it in bulk, and stick to it, using a head cleaning tape if they change tape brand.